Power train control system

ABSTRACT

A control system is shown for a multispeed forward and reverse track-laying vehicle power train, the control system having a manual forward and reverse control for effecting manual shifts between forward and reverse, a manual drive range control and an automatic drive range control for effecting manual and automatic drive-range-shifting operation and a steering control for effecting steering operation. The manual forward and reverse control provides selection between forward and reverse drive in the lowest drive range and prevents such shifting by the operator in all of the higher drive ranges. The manual drive range control provides selection between the drive ranges with the selected drive range being established immediately on an upshift and by speed governed automatic shifting operation on a downshift. The automatic drive range control provides automatic shifting using separate speed-controlled upshift biases, an engine-torquedemand-controlled upshift-inhibiting bias and an engine-torquedemand-controlled downshift bias. Both the manual forward and reverse control and the manual drive range control are electrically activated and in the event there is an interruption in electrical power, the directional drive selected by the manual forward and reverse control is maintained while the range control, if under manual control, is automatically conditioned for automatic control to maintain power train control. A sequence control is effective to disengage the range drive to the load in the lowest drive range during shifting between forward and reverse to provide for engagement of the directional drive under no-load conditions. The steer control operates on a hydrostatic unit to control steering by controlling hydrostatic pump displacement while assuring straight vehicle no-drift motion when there is no steer demand. The controlling force effecting this pump displacement control is varied according to hydrostatic pump output to meet the varying steer load demands in both directions of steer. There is also provided a stroke or pump displacement limiter for limiting pump displacement regardless of the steer demanded by the operator to prevent pump overload. Hydrostatic system pressure is controlled by a pressure relief control in accordance with the engine torque demand and vehicle speed to both prevent overloading of the hydrostatic pump and limit the degree of steer bias. The steer control signals the range control to inhibit automatic range shifting during steering operation. The hydrodynamic torque converter in the power train has a lockup drive which is normally disengaged on range shifting and is held engaged during low speed operation in each range to provide for utilization of vehicle momentum to provide power for steering while preventing engine stall.

nited States Patent Schaefer [54] POWER TRAIN CONTROL SYSTEM [72]Inventor: Robert H. Schaefer, Westfield, Ind.

[73] Assignee: General Motors Corporation, Detroit,

Mich.

221 Filed: Nov. 27, 1968 211 Appl. No.1 779,502

52 U.S.Cl ....-.74/s69,60/53,74/752,

18016.2, 192/3. v 51 1m. 01. ..B60k2l/06, B62dll/l0,Fl6d 67/00 58FieldofSearch ..-....74/867,s6s, 869, 752

[56] ReferencesCited V UNITED STATES PATENTS, 2,606,456 8/1952 Dodge.....'....74/s67x 2,711,656 6/1955 Smirl 74/86s-x 2,740,303 4 1956 Bock 61.al..... Li.74/869 2,761,328 9 1956 l-lerndon etal. ..74/869 3,053,1169/1962 Christenson etal. ...;..74/s68x 3,056,313 10/1962 Lindsay 74/7523,077,122 2 1963 3,078,736, 2/1963 Meads 6:61. ;74l867 3,159,051 12/1964Herndon et a]. ..74/869 X 3,439,564 4/1969 Scholl et a1. ...74/752 x3,505,906 4/1970 Lemieux ..74/869 x Primary Examinerwilliam L. FreehAssistant ExaminerThomas C. Perry AttorneyE. W. Christen, A. M. Heiterand R. L. Phillips [57] ABSTRACT ing manual and automaticdrive-range-shifting operation and a [451 Feb. 8, 1972 steering controlfor effecting steering operation. The manual drive range controlprovides automatic shifting using separate speed-controlled upshiftbiases, an engine-torque-demandcontrolled upshift-inhibiting bias and anengine-torque-demend-controlled downshift bias. Both the manual forwardand reverse control and the manual drive range control are electri- 1cally activated and in the event there is an interruption in electricalpower, the directional drive selected by the manual forward and reversecontrol is maintained while the range control, if under manual control,is automatically conditioned for automatic control to maintain powertrain control. A sequence control is effective to disengage the rangedrive to the load in the lowest drive range during shifting betweenforward and reverse to provide for engagement of the directionaldriveunder no-load conditions. The steer control operates on ahydrostatic unit to control steering by controlling hydrostatic pumpdisplacement while assuring straight vehicle nodrift motion when thereis no steer demand. The controlling force effecting this pumpdisplacement control is varied according to hydrostatic pump output tomeet the varying steer I load demands in both directions of steer. Thereis also provided a stroke or pump displacement limiter for limiting pumpdisplacement regardless of the steer demanded by the operator to preventpump overload. Hydrostatic system pressure is controlled by a pressurerelief control in accordance with the engine torque demand and vehiclespeed to both prevent overloading of the hydrostatic pump and limit thedegree of steer bias. The steer control signals the range control toinhibit automatic range shifting during steering operation. The

hydrodynamic torque converter in the power train has a lockup drivewhich is normally disengaged on range shifting and is held engagedduring low speed operation in each range to provide for utilization ofvehicle momentum to provide power for steering while preventing enginestall.

11 Claims, 9 Drawing Figures WWW @1912 3,640.15?

SHEET 1 0F 6 w 25,212 .fiZaZa 25;] 1% @zmyz PRIME MOVER 559 Gl GOVERNORif;

VALVE ATTORNEY Wm Fl? 81972 3640,15?

SHEU 2 UP 6 MANUAL SIGNAL VALVE G. l. ACCUMULATOR l-Z SHIFT VALVE 3' 4SHIFT VALVE NEUTRAL SHIFT VALVE INVliN'l (1K.

AT TORNEY SHEET 3 BF 6 AUTOMATIC SHIFT INHIBITOR VALVE AIR VALVE .V. AL

LOCKUP VALVE AND REVERSE MAIN PRESSURE REGULATOR VALVE COOLER REGULATORVALVE IN VEN TOR.

AT TORNEY sum 14 0F 6 HYDROSTATIC PUMP HYDROSTATIC MOTOR CENTERING ANDSTEER SIGNAL DEVICE INVEN'I'UR,

ATTORNEY PATENTED FEB 8 I972 3.640.157

sum 5 OF 6 FOEWARD AND SEQUENCE VALVE FORWARD AND REVERSE SHIFTINHIBITOR VALVE RELI EF VALVE MODULATOR VALVE INVEN'] 0k.

, @0502 H, Scaefer AT TORN EY PATENTED 8:912 3340.157

TRAN$M|SS|ON SOLENOID VALVE RANGE 774 952 9|8 803 798 7|6 7|5 FAUTOMATIC X o 4 X x R 3 X X X X 2 x x g l I X X NEUTRAL x x R AUTOMATICx 5 E 4 X X \E/ 3 X X x INVEN'IOR. R 2 x x Hafiz/'2 H Scfiaefi'r 5 I X XBY E I X 5.0%?

ATTORNEY POWER TRAIN CONTROL SYSTEM This invention relates to powertrain or transmission control systems and more particularly to a controlsystem for a tracklaying vehicle power train providing manual shiftcontrol, automatic shift control and steering control.

The control system according to the present invention may be employed intrack-laying vehicle power trains or transmissions of the type shown inUS. Pat. No. 3,373,636 issued Mar. 19, 1968, to Livezey et al. andentitled VEHICLE TRANS- MISSION INCLUDING STEERING BY DRIVING. Thecontrol system includes an upstream and a downstream main pressureregulator valve, the former regulating pressure at a value modulatedaccording to both drive range and torque converter operation and usedprimarily for drive range engagement and converter lockup and the latterregulating pressure at an unmodulated value used primarily fordirectional drive engagement, control functions and as a source forcontrol pressures. Two fluid velocity governors are provided, oneproducing a governor pressure (G1) proportional to converter turbine andpower train output speed and the other producing a governor pressure(G2) which is zero throughout the lowest drive range and proportional torange unit and power'train output speed in all of the higher driveranges. A pair of throttle pressure regulator valves provide threecontrol pressures, two of these control pressures (T and TV) derived byone valve from the unmodulated main pressure and the remaining controlpressure (range TV) derived by the other valve from the unmodulated mainpressure and TV pressure. The TV pressure is proportional to enginethrottle opening, T pressure is the upper portion of the TV pressurerange, and range TV pressure has a predetermined minimum value and isotherwise equivalent to TV pressure. A lockup valve under the control ofimplementing G1 pressure and inhibiting T and TV pressure determinesconverter lockup with a flow valve normally interrupting lockup duringrange shifting and a flow valve modulator valve under the control of TVpressure overriding the normal flow valve operation to permitmaintenance of lockup with G1 pressure during range downshifting below apredetermined TV pressure or part engine throttle opening. A neutralshift valve under the control of a manually controlled solenoid valvedetermines the delivery of the modulated main pressure to seriesarranged range shift valves for driverange engagement.

The range shift valves operate to automatically shift between the-driveranges under the control of an upshift bias by G1 pressure for thelowest upshift, an upshift bias by G2 pressure for the higher upshifts,an upshift inhibiting bias by range TV pressure and a downstream bias byT pressure. The range shift valves under the control of manuallycontrolled solenoid valves provide for manual range selection. Formanual range selection, a manual signal valve under the control ofmanually controlled solenoid valves substitutes unmodulated mainpressure for the T pressure downshift bias on the proper range shiftvalves to provide automatic downshifting from any higher drive rangethrough. any intennediate drive range to the manually selected driverange. This automatic downshifting with manual drive range selection iscontrolled to occur at a vehicle speed suitablefor each lower driverange as determined by governor pressure bias, upshifts by manualselection occurring immediately.

A forward and reverse shift valve under the. control of manuallycontrolled solenoid valves determines the delivery of unmodulated mainpressure for directional dn've engagement in the selection being betweenforward and reverse drive. A forward and reverse inhibitor valve underthe control of G2 pressure permits shifts between forward and reverse inthe lowest drive range and prevents such shifting in all of the higherdrive ranges. A sequence valve under the control of the operation of theforward and reverse shift valve effects disengagement of the drive tothe load during a directionalchange in the lowest drive range to pennitengagement of the directional drive under no-load conditions. Anautomatic shift inhibitor valve under the control of a steer signalpressure from the steer control inhibits automatic shifting duringsteering operation. There is also provided in the control system aconverter pressure regulator valve which limits pressure to the torqueconverter, this pressure being modulated in accordance with converteroperation, and an air valve which controls delivery of fluid tohydrodynamic and hydromechanical output brakes.

All of the solenoid valves are controlled by the operator from aselector box with a forward and reverse shift lever controlling solenoidvalve operation for directional change and the remainingsolenoid valvescontrolled by a manual and automatic shift lever for both manual driveselection and automatic range shifting. The solenoid valves areconnected in the control system such that when they are all deenergized,the control system is conditioned for automatic range shifting in eitherdrive direction, the forward and reverse shift valve being mechanicallydetented in each of its two drive determining positions. For automaticshifting operation, the forward and reverse shift lever is controlled bythe operator to select the drive direction desired by energization ofthe proper direction control solenoid valve while the manual andautomatic shift lever is operated to deenergize the remaining solenoidvalves. Manual drive range selection .is made by operating the manualand automatic shift lever to energize the proper solenoid valves toestablish the desired drive range while the forward and reverse lever isoperated to detennine drive direction. Thus, with this arrangement andin the event there is an interruption in the electrical power whileoperating with manual drive selection, the control system will beautomatically conditioned for automatic range shifting in the directionpreviously determined so that range shifting remains available.

The steer bias of the power train is effected by a converter pump drivenhydrostatic unit, hydrostatic pump displacement being controlled bysteer controls in the control system to control the'steer bias. Amanually controlled steer valve controls the delivery of a controlpressure to vary-hydrostatic pump displacement, the steer valveproviding pump displacement in proportion to manual steer input. Acentering and steer signal device accurately positions the steer valvefor zero pump displacement and thus no steer bias when a steer is notbeing demanded and supplies the steer signal pressure to the automaticshift inhibitor valve for inhibiting automatic shifting during steeringoperation. A control pressure regulator valve always responsive tohydrostatic pump output pressure modulates the control pressurecontrolling pump displacement so that it increases with increasinghydrostatic pump output pressure and thus steer effort. An overloadstroke limiter valve under the control of the pressure differentialacross the hydrostatic pump overrides steer control to prevent steerbias which would overload the hydrostatic pump. A relief valve is alwaysconnected to limit hydrostatic pump output pressure. The relief valve isunder the control of a control pressure from a relief valve modulatorvalve which is controlled by range TV pressure and G2 pressure. In thelowest drive range the relief valve modulator valve control pressure tothe relief valve controls maximum hydrostatic pump output pressure inaccordance with range TV pressure to prevent pump overload and controlpump power absorption to prevent engine stall. In all of the higherdrive ranges the maximum hydrostatic pump output pressure in addition tothe throttle pressure control is caused to decrease with increasing G2pressure to prevent overloading the hydrostatic pump during demandedhigh speed turns.

An object of the present invention is to provide a new and improvedpower train control system.

Another object is to provide a new and improved power train controlsystem providing both manual and automatic shifting.

Another object is to provide a power train control system having both amanual shift control and an automatic shift control wherein theautomatic shift control remains available on discontinuance of power tothe manual control.

Another object is to provide in a power train control system a torqueconverter lockup control for interrupting lockup during range shiftingwhile holding lockup from zero to part engine throttle at low vehiclespeeds.

Another object is to provide in a power train control system a sequencecontrol to disengage a range drive on a directional change to permitdirectional drive engagement under no-load conditions.

Another object is to provide in a power train control system a manualshift control with automatic downshifting according to vehicle speed toa selected lower drive range.

Another object is to provide in a power train control system adirectional drive inhibitor inhibiting directional changes in the powertrains high drive ranges.

Another object is to provide in a power train range and steer controlsystem a shift inhibitor inhibiting automatic shifting during steeringoperation.

Another object is to provide in a power train control system anunmodulated main pressure source for directional drive engagement,control functions and control pressures and a modulated main pressuresource for drive range engagement and converter lockup.

Another object is to provide in a power train control system multiplethrottle pressures for different control functions including converterlockup range shifting and hydrostatic pressure relief.

Another object is to provide in a hydrostatic steer control of a powertrain control system a control pressure regulator modulating controlpressure for steer bias according to hydrostatic pump output pressure.

Another object is to provide in a hydrostatic steer control of a powertrain control system an overload stroke limiter limiting hydrostaticpump displacement in accordance with differential pressure across thehydrostatic pump.

Another object is to provide in a hydrostatic steer control of a powertrain control system a maximum hydrostatic pump output pressure reliefin accordance with engine throttle opening and vehicle speed.

Another object is to provide in a power train control systemelectrically actuated manual drive selection and automatic driveselection independent of electrical power.

Another object is to provide in a power train control system anelectrically actuated manual range selection and directional drive and afluid pressure actuated automatic range control automatically actuatedon discontinuance of electrical power for manual selection whiledirectional drive selection is maintained.

These and other objects of the present invention will be more apparentfrom the following description and drawings in which:

The power train and control system are shown schematically in FIGS. 20,2b, 2c, 2d and 2e, when arranged as indicated by FIG. 1.

FIG. 3 is a view taken on the line 3-3 in FIG. 2d.

FIG. 4 is a perspective view with parts broken away of the operatorscontrol in the power train control system.

FIG. 5 shows the schedule of power train operation.

POWER TRAIN ARRANGEMENT The invention is illustrated in an arrangementcontrolling a track-laying vehicle power train which is of the typeshown in detail in the Livezey et al. US. Pat. No. 3,373,636 and iscapable of providing multiple speed or drive range and hydrostaticsteering operation in forward and reverse. The power train as shown inFIGS. 2a and 2d receives input from a prime mover 210 such as a pistonengine and generally comprises a hydrodynamic torque converter 211, aforward and reverse drive unit 212, a three-speed planetary gear rangeunit 213, a left steer unit 214, a right steer unit 216, a differentialunit 218, and a hydrostatic pump and motor steer unit 219 forcontrolling differential unit 218, all housed in a housing 222. Thesecomponents are connected in the power train arrangement to provide fourspeed or drive ranges in forward and reverse and hydrostaticallycontrolled steering.

In the power train arrangement, the engine 210 is con nected to drivethe power trains input shaft 224 which is connected by the convertersrotary housing 226 to pump blading 228 (P). The pump blading 228 exitsfluid to turbine blading 229 (T) which is connected by hub 231 toconverter output shaft 232. Fluid is redirected to pump blading 228 bystator blading 234 (S) which is grounded to the power train housing forreaction by one-way brake 236. A converter lockup clutch 238 connectedbetween converter housing 226 and hub 231, when engaged, provides directmechanical drive between power train input shaft 224 and converteroutput shaft 232.

The converter output shaft 232 provides input to both the range unit 213and the differential unit 218 via the forward and reverse drive unit212, the range unit 213 providing one input to each of the steer units214 and 216 and the differential unit 218 providing another input toeach of the steer units. In the drive to forward and reverse drive unit212, the converter output shaft 232 is connected at its left end to agear 239 meshing with an idler gear 240. Idler gear 240 meshes with agear 241 which latter gear is connected to a shaft 242. Shaft 242 isconnected to clutch drum 244 of the forward and reverse drive unit 212.Drum 244 is connectable through either a forward or reverse drive toboth the range unit 213 and differential unit 218. For the forward driveunits 213 and 218, unit 212 has a forward drive clutch 246 which, whenengaged, connects drum 244 to a gear 247 geared to drive an annular gear248. In this gear drive, gear 247 meshes as illustrated schematically bythe dashed line with an idler gear 245 which latter gear meshes with thegear 248. Gear 248 is connected to a sleeve shaft 249 which is the inputshaft or range unit 213. Gear 247 also meshes with an annular gear 250which is connected to drum 251 of the differential unit 218, unit 218being described in more detail later. Thus, in the forward drive geartrain provided and with the forward drive clutch 246 engaged, shaft 242drives the range unit input shaft 249 in the same direction and thedifferential drum 251 in the opposite direction.

For the reverse drive to the units 213 and 218, a reverse drive clutch252 in unit 212 is engaged to connect drum 244 to an annular gear 254freely received on shaft 242. Gear 254 meshes with an idler gear 256which meshes with an annular gear 257. Gear 257 is connected by thedifferential drum 251 to the gear 250 at the other end of the drum. Thedrive is then from gear 250 via gears 247, 245 and 248 to the range unitinput shaft 249. Thus, with the reverse drive clutch 252 engaged, shaft242 drives the range unit input shaft 249 in the opposite direction andthe differential drum 251 in the same direction.

In the range unit 213, its input shaft 249 is connected to both theannular sun gear 258 of a low-ratio planetary gear set 259 and theannular sun gear 261 of an intermediateratio planetary gear set 262. Thesun gear 258 meshes with pinions 264 journaled on an output carrier 266.Ring gear 268 of the low-ratio gear set meshes with pinions 264, isconnected to carrier 269 of the intermediate-ratio gear set, and may beheld by a low brake 271 to provide a low-ratio drive to output carrier266. The sun gear 261 of the intermediate-ratio gear set meshes withpinions 272 joumaled on carrier 269. Ring gear 274 of theintermediate-ratio gear set meshes with pinions 272 and may be held byan intermediate brake 276 to provide higher speed and intermediate-ratiodrive to output carrier 266. A high clutch 278, when engaged, connectsthe range unit input shaft 249 to the intermediate carrier 269 andconnected low ring gear 268 to lock the low-ratio gear set 259 toprovide direct drive between the range unit's input and output.

The range unit output carrier 266 is connected by a hub 279 to rangeunit output shaft 280 which extends freely through sleeve shaft 249,shaft 280 serving as both the range units output shaft and the steerunits input shaft. Shaft 280 is connected at its left end to ring gear281 of a planetary gear set 282 in left steer unit 214 and at its rightend to ring gear 284 of a planetary gear set 286 in right steer unit216, gear sets 282 and 286 having equal speed ratios.

On the left side, the ring gear 281 of gear set 282 meshes with pinions287 journaled on an output carrier 288. An annular sun gear 290 freelyreceived on shaft 280 meshes with pinions 287 and is connected to becontrolled by the differential unit 218 as described in more detaillater. A drum 291 connects carrier 288 to the power trains left outputshaft 292 which shaft is for powering the vehicles left track. Amechanical brake 299 and a hydrodynamic brake 300 are both connected tobrake the power trains left output shaft 292.

On the right side, the ring gear 284 of gear set 286 meshes with pinions301 journaled on an output carrier 302. A drum 303 connects carrier 302to the power trains right output shaft 304 for powering the vehiclesright track. An annular sun gear 306 freely received on shaft 280 mesheswith pinions 301 and is connected to be controlled by the differentialunit 218. A mechanical brake 316 and a hydrodynamic brake 317 are bothconnected to brake the power trains right output shaft 304.

A low low brake 318, when engaged, is connected by the hub 279 to holdshaft 280 and the connected ring gears 281 and 284 of the steer units.This enables the sun gears 290 and 306 of the steer units to producedrive in the steer units without output from the range unit and at thelowest available ratio as described in more detail later.

Describing the hydrostatically controlled differential unit 218, the sungears 290 and 306 of the steer units are continuously connected by equalspeed ratio and direction reversing gear trains to output carriers 322and 324 of equal speed ratio planetary gear sets 326 and 328,respectively, provided in unit 218. The left gear train comprises anannular gear 325 which is connected to sun gear 290 of the left steerunit and meshes with an annular gear 323. Gear 323 is connected by asleeve shaft 327 to the left output carrier 322 of unit 218. The rightgear train similarly comprises an annular gear 328 which is connected tosun gear 306 of the right steer unit and meshes with an annular gear329. Gear 329 is connected by a sleeve shaft 330 to the right outputcarrier 324 of unit 218. The ring gears 331 and 332 of gear sets 326 and328 are both connected to the drum 251 driven by the forward and reversedrive unit 212. Pinions 334journaled on the left output carrier 322 meshwith the ring gear 331 and a sun gear 336. Similarly, pinions 338joumaled on the right output carrier 324 mesh with the ring gear 332 andan annular sun gear 339. The sun gears 336 and 339 mesh with meshingdifferential pinions 341 and 342, respectively. The differential pinions341 and 342 are journaled on spindles attached to a differential carrier344 which is continuously grounded to the power train housing by a shaft346 which extends through annular sun gear 339.

Hydrostatic control of differential unit 218 is provided by thehydrostatic unit 219 shown in FIG. 2d operating on sun gear 336 ofdifferential unit 218 which sun gear is connected by a shaft 349 to agear 351, shaft 349 extending through sleeve shaft 327 to make theconnection. Gear 351 meshes with a gear 352 which latter gear isconnected by a motor output sleeve shaft 354 to the hydrostatic motor356. The hydrostatic pump 358 is input driven through a gear train whichhas an annular gear 359 connected to the converter housing 226 andmeshing with an idler gear 361. Gear 361 meshes with an annular gear 365which is connected by a pump input sleeve shaft 367 to the hydrostaticpump 358, the input shaft 242 of the forward and reverse drive unit 212extending freely through both shafts 367 and 354. Preferably, thehydrostatic pump 358 and hydrostatic motor 356 are axially aligned asone unit and located between the gears 365 and 352 with their centralaxis coinciding with that of the shaft 242 which then extends freelythrough the hydrostatic pump and motor steer unit. The pump 358 has avariable displacement and the motor 356 has a fixed displacement and thehydrostatic unit is conditionable to hold motor output shaft 354 and todrive the motor output shaft in either direction at infinitely variablespeed.

The drive-producing clutches and brakes are conventional frictiondrive-establishing devices of the friction plate type each having asuitable fluid motor which is operated by fluid pressure to efiectengagement of the device. Each of these devices also has suitableretraction spring means, not shown, that operate on exhaust of the fluidpressure to effect disengagement of the device. The output mechanicalbrakes 299 and 316 have conventional structure and are operatedsimultaneously by conventional linkage which includes a rotary orotherwise movable member such as shaft 370 shown in FIG. 20 which shaftturns during engagement and disengagement of these brakes.

OPERATION OF POWER TRAIN ARRANGEMENT The power train may be operated toprovide four speed or drive ranges in forward and reverse andhydrostatically controlled steering. The first l) or low low drive rangewhich is considered the lowest drive range and provides the greatesttorque multiplication is established by engaging the forward driveclutch 246 in the case of forward drive and the low low brake 318 andconditioning the hydrostatic steer unit 219 to hold the motor outputshaft 354 and thus the controlled sun gear 336 in differential unit 218,all other drive-establishing devices being disengaged. Since the carrier344 in the differential unit is grounded and the sun gear 336 is held bythe hydrostatic steer unit, rotation of the other sun gear 339 is alsoprevented. With ring gears 331 and 332 of the differential unit beingdriven at the same speed and in the same direction by converter 211through the forward drive clutch 246, the differential output carriers332 and 324 are driven in the same direction at the same speed by lockeddrives. Thus, the sun gears 290 and 306 of steer units 214 and 216 aredriven in the same direction which is forward and at the same speedwhile both of the ring gears 281 and 284 of the steer units are held bythe low low brake 318. Therefore, the gear sets 282 and 286 in the steerunits act as reduction gear sets with the locked input drives thusprovided to drive the power train output shafts 292 and 304 in theforward direction at the same speed. When the speed of the converterturbine 229 reaches a desired value the lockup clutch 238 is engaged toprovide mechanical drive instead of the hydraulic drive through theconverter.

In the difi'erential unit 218, rotation of sun gear 336 in eitherdirection with the infinitely variable speed drive made available by thehydrostatic steer unit 219 results in opposite rotation of sun gear 339at the same speed. Thus, the output carriers 322 and 324 and their geartrain connected sun gears 290 and 306 of the steer units are driven atequal differential speeds measured from their same base speed with sungear 336 held since the speed of these carriers is determined by thecombination of the equal speed ratio drive to the connected ring gears331 and 332 and the equal speed opposite directional drive to the sungears 336 and 339..

Thus, for steering in the first forward drive range the hydrostaticsteer unit 219 is conditioned so that instead of continuing to hold thedifferential units sun gear 336, it then drives the controlled sun gear336 in either direction depending on the direction of vehicle turndesired. Then, with sun gear 336 rotating in one direction, the otherdifferential sun gear 339 is caused to rotate in the opposite directionat the same speed. The combined differential action in the gear sets 326and 328 that results causes, as for example when sun gear 336 is drivenin the same direction as the ring gears 331 and 332, the carrier 322 tospeed up by the same amount that the carrier 324 is being slowed down.In this manner the sun gears 290 and 302 in the steer units aredifferentially driven in the same direction or in opposite directionswith locked differential drives, recognizing that the left sun gear 290,for example, will be speeded up by the same amount that the speed of theright sun gear 306 is diminished to thereby establish the differentialsteering. The steering radius is thus put under positive control andmade infinitely variable by units 218 and 219 from straight ahead drivein the first drive range down to the minimum radius possible withgearing provided.

The three higher drive ranges (2, 3, 4) in the forward direction areestablished by driving the connected ring gears 281 and 284 in the steerunits forward at different speeds with the forward clutch 246 remainingengaged, the sun gear 336 of the differential gear unit 218 held by thehydrostatic steer unit 219 and selective conditioning of the range unit213 to provide its low-ratio drive (low brake 271 engaged),intermediate-ratio drive (intermediate brake 276 engaged), andhigh-ratio drive (high clutch 278 engaged) in that order. In these threehigher drive ranges, the steer units then act as power combining andspeed differential devices receiving power from both the rang unit 213and the differential unit 218. Hydrostatically controlled diflerentialsteering is available in these higher ranges by control of thehydrostatic steer unit 219 to provide locked differential drive asdescribed in the first drive range, recognizing that the speed added toone of the steer unit sun gears will be equal to the speed subtractedfrom the opposite steer unit sun gear while the connected ring gears ofthe steer units continue to rotate forwardly with their drive from rangeunit 213. Thus, the output speed in one steer unit is increased by theamount the output speed of the other steer gear unit is diminished toprovide the differential steering. Again, the steer radius is underpositive control and infinitely variable in the second, third and fourthforward drive ranges from straight ahead down to the minimum radiuspossible with the gearing provided.

Since the forward and reverse drive unit 212 provides the input to boththe range unit 213 and differential unit 218, the same drive ranges andhydrostatically controlled differential steering provided in forward asdescribed above, are also available in reverse by simply disengaging theforward drive clutch 246, engaging the reverse drive clutch 252 andoperating range unit 213 and hydrostatic steer unit 219 as before.

For neutral, either the forward or reverse drive clutch is preferablyengaged, all other drive establishing devices are disengaged, the sungear 336 of the differential unit 218 is held by the hydrostatic steerunit 219 and there is no output drive to the power train output shafts292 and 304. Steering in neutral is provided by controlling thehydrostatic steer unit 219 to drive the sun gear 336 in the differentialunit 218 in either direction dependent on the direction of vehicle turndesired. This causes the opposite sun gear 339 of the differential gearunit to rotate in the opposite direction at the same speed and since thedrum 251 is acted on by opposed gear forces, the connected ring gears331 and 332, though free, provide reaction in their gear sets. Thus, theoutput carriers 322 and 324 of the differential unit are caused torotate at equal speeds in opposite directions. Because the sun gears 290and 306 of the steer units are being driven in opposite directions andat the same speed by the free differential drives provided by unit 218,the connected ring gears 281 and 284 of the steer units, though free,provide reaction resulting in the power train output shafts 292 and 304being driven at equal speeds in opposite directions to produce pivotsteering.

CONTROL SYSTEM The control system for this power train arrangement andaccording to the present invention provides for both automatic andmanual selection of the four drive ranges in both forward and reverseand steering control in all drive ranges and neutral. Other functions ofthe control system include lubrication, cooling, charging of the torqueconverter, and charging of the hydrodynamic brakes.

FLUID SUPPLY The fluid such as oil used in all of the control functionsis supplied by four gear-type positive displacement pumps shown in FIG.which draw from a reservoir 400 to which the fluid exhaust from allparts of the system is returned. Fluid which tends to accumulate incertain locations in the power train housing 222 is scavenged by one ormore input driven scavenge pumps, not shown, which remove this excessfluid and return it to the reservoir.

The pump 402 which is called the hydrostatic superchargeconverter pump,is drivingly connected to the power train input shaft 224 so that it iscontinuously driven to supply fluid when the engine is operating. Thispump supplies both the hydrostatic steer portion and the torqueconverter portion of the system.

The pump 404, which is called the coolant pump, is drivingly connectedto the converter turbine 229 so that it is driven to supply fluid whenthe converter turbine is being driven. The fluid supplied by this pumpis delivered to charge the hydrodynamic output brakes 330 and 317 withthis same fluid then being used to flood the friction plates of themechanical output brakes 299 and 316 to cool them during theirengagement.

The pump 406, which is called the main pressure input pump, is drivinglyconnected to the power train input shaft 224 so that it is continuouslydriven to supply fluid when the engine is operating. The fluid suppliedby this pump furnishes the main fluid supply to the shift controlportion of the control system which controls the shifting of the powertrain and also delivers fluid to lubricate various parts of the powertrain.

The pump 408, which is called the main pressure output pump, isdrivingly connected to one of the power train output shafts, outputshaft 292 for example, so that it is driven to supply fluid only whenthe vehicle is moving forwardly. The fluid supplied by this pumpsupplements the fluid supply from the main pressure input pump 406during forward drive operation and is the only source of main pressuresupply when the main pressure input pump is not operating.

HYDROSTATIC SUPERCHARGE PRESSURE REGULATOR VALVE The hydrostaticsupercharge-converter pump 402 draws fluid from the reservoir 400 viaintake line 410 and delivers this fluid to a hydrostaticsupercharge-converter supply line 412. Line 412 as shown in FIG. 2a isconnected to a chamber 414 in one end of the valve body of a hydrostaticsupercharge pressure regulator valve 416 which in addition to providinga regulated low-pressure source for the hydrostatic portion of thecontrol system admits fluid to the torque converter 211. Regulator valve416 has a regulator valve element 418 with a land a located in bore 420of a sleeve 422 secured in the valve body. A valve stem 424 bottomed ona retaining ring 426 has a land a located in a blind bore 428 in thelower end of regulator valve element 418 to provide a damping chamber430. Chamber 430 is continuously connected by an orifice 432 and anelongated annular channel 433 in regulator valve element 418 to thecontrol systems main line which has fluid at main pressure as describedin more detail later.

The force of a spring 434 arranged between the regulator valve element418 and the base of the valve stem 424 plus the main pressure in dampingchamber 430 urge the regulator valve element 418 upward toward theclosed position shown, the closed position determined by shoulder 436 ofvalve element 418 abutting collar 438 of sleeve 422. The regulator valveelement 418 in its closed position closes a converter-in line 440 fromthe hydrostatic supercharge-converter supply line 412. These forces areopposed by the pressure from line 412 acting on the full upper end areaof land a of regulator valve element 418 which urges the regulator valveelement downward toward an open position connecting line 412 to theconverter-in line 440 through porting 441 in sleeve 422. The spring biasof the regulating spring 434 plus the pressure bias in chamber 430provide for regulation of pressure (hydrostatic supercharge pressure) inline 412 to the desired value with the overage delivered to theconverter-in line 440. The damping chamber 430 with its restrictedconnection by orifice 432 to the control systems main line prevents theshoulder 436 from battering the collar 438 during the pressureregulation.

CONVERTER PRESSURE REGULATOR VALVE The pressure of the fluid admitted bythe hydrostatic supercharge pressure regulator valve 416 to theconverter-in line 440 is reduced to either one of the two lowerregulated pressures by a converter pressure regulator valve 442 shown inFIG. 2a. The high regulated pressure provided by the converter pressureregulator valve 442 is for normal converter operation and the lowregulate pressure is for lockup operation with the lockup clutch 238engaged. The converter-in line 440 is connected to a chamber 444 in theupper end of the valve body of regulator valve 442 which has a regulatorvalve element 446 guided by a rod 448 extending through central bore 450in the valve element. The rod 448 is secured at its lower end to a plug452 located in bore 454 of the valve body, plug 452 in cooperation withbore 454 providing a chamber 456. A spring 458 arranged between theregulator valve element 446 and plug 452 urges the regulator valveelement upward toward the closed position shown. The regulator valveelement 446 in its closed position closes the chamber 444 and connectedconverter-in line 440 from an exhaust 460. The closing force is opposedby pressure from the converter-in line 440 acting in chamber 444 on theregulator valve element 446, this pressure urging the regulator valveelement downward toward an open position connecting the chamber 44 toexhaust 460. The low regulated pressure is provided when the chamber 456is exhausted and the plug 452 is hottomed so that the normal bias ofregulating spring 458 determines the opening and closing of the valve.

The high regulated pressure by converter pressure regulator valve 442 isprovided when a pressure signal is delivered to the chamber 456 from thelockup shift control portion of the control system as described in moredetail later. The pressure delivered to chamber 456 raises the plug 452upward to the position shown in which it abuts with a stop ring 461thereby increasing the bias applied by spring 458 to the regulator valveelement 446 to effect the high-pressure regulation. An elongatedexternal annular channel 462 in the plug 452 is supplied with fluid fromthe control systems main line described later so that the plug floats ona constant film of fluid allowing it to move readily between its low andhigh-pressure positions.

The fluid at pressure regulated by the converter pressure regulatorvalve 442 is delivered by the converter-in line 440 to the torqueconverter 211. The fluid leaves the converter by a converter-out line464 which passes it through a cooler 466 located externally of the powertrain housing prior to returning it to the reservoir 400, therestriction to flow through the converter-out line 464 and cooler 466maintaining pressure at the converter outlet.

The capacity of the hydrostatic supercharge-converter pump 402 issufficient to meet the requirements of both the hydrostatic portion ofthe control system and the torque converter during all their operatingconditions, the high charging pressure for converter operationmaintaining the converter filled with fluid while effecting sufficientflow to carry away heat for dissipation in the cooler. During lockupoperation, the converter requires a smaller volume of fluid which iseffected by the low regulated pressure provided by the converterpressure regulator valve 442.

HYDRODYNAMlC BRAKES The coolant pump 404 is operable to draw fluid fromthe reservoir 400 via an intake line 468 through a check valve 470 anddeliver the fluid to a coolant line 472 as shown in FIG. 2c. Coolantline 472 is connected to cavities 474 and 476 of the hydrodynamic brakes300 and 317, respectively, as shown in FIG. 2a. With rotors 478 and 480of the hydrodynamic brakes 300 and 317, respectively, rotating throughtheir fluid-filled cavity, there is provided hydrodynamic braking of thepower train output shafts. When pump 404 is operating the fluidcontinuously passes through the cavities 474 and 476 and is directed bymechanical brake coolant lines 482 and 484 to cool the friction platesof the mechanical output brakes 299 and 316, respectively.

AIR VALVE Control over delivery of fluid by the coolant pump 404 to thehydrodynamic and mechanical output brakes is provided by an air valve486 shown in FIG. 2c. Air valve 486 has a valve element 488 which in theopen position shown opens chamber 490 in the valve body via a port 491to an airline 492, chamber 490 being open to atmosphere. Airline 492 isconnected to the intake side of the coolant pump 404 upstream of checkvalve 470. Thus, when the coolant pump is being driven with the airvalve 486 open, the check valve 470 closes and the coolant pump is airbled and delivers only air to the cavities of the hydrodynamic andmechanical output brakes'thereby belljarring these cavities to force anyfluid therein back to the reservoir. When theair valve element 488 ismoved to a closed position closing port 491 and thus closing the airline492 to the atmospheric chamber 490, air is prevented from entering theintake side of the coolant pump which then operates to draw fluidthrough the check valve 470 for delivery to the brakes.

The opening and closing of the air valve 486 is under the control of themechanical linkage which operates the mechanical output brakes 299 and316. The valve element 488 is secured to the upper end of a right-anglearm 494 which is pivoted at its bend on a pivot pin 496 secured in thevalve body. The lower end of arm 494 has an aperture through which acontrol rod 498 extends, the rod being mounted for reciprocal movementin stepped bore 499 in the valve body. When the mechanical output brakesare disengaged, shaft 370 of their linkage is in the angular positionshown in FIG. 2c. An arm 500 splined to shaft 370 engages the projectingleft end of control rod 498 so that while the mechanical output .brakesare disengaged, a spring 502 mounted in a bore 503 in the valve body andbetween a screw plug 504 and the lower end of arm 494 holds the latteragainst a collar 506 on the control rod 498. This positions and holdsthe valve element 488 in its open position so that the coolant pump 404is air bled when the mechanical output brakes are disengaged. When themechanical output brakes are engaged by the operator, shaft 370 ispivoted counterclockwise as shown by the directional arrow. This swingsarm 500 counterclockwise and the spring 502 forces the control rod 498to follow arm 500 while forcing the lower end of arm 494 to follow thecollar 506 and swing valve element 488 to its closed position, thecollar 506 abutting shoulder 501 in bore 499 to limit the leftwardmovement of the control rod. With the air valve 486 closed the coolantpump 404 is no longer air bled and then delivers fluid to the brakes aspreviously described. The motion of the mechanical linkage operating themechanical brakes is such that the air valve 486 closes prior to initialengagement of the mechanical output brakes so that the hydrodynamicbrakes are put in operation first to retard the vehicle.

MAIN PRESSURE REGULATOR VALVE The main pressure input pump 406 drawsfluid from the reservoir 400 via intake line 508 and delivers this fluidto a main line 510. The main pressure output pump 408 draws fluid fromthe reservoir via an intake line 512 and delivers this fluid through acheck valve 514 to main line 510. The fluid delivered to main line 510from these pumps is passed through a filter 516 prior to flowing to alldownstream portions of the control system.

The main pressure supply for the shift control portion of the controlsystem is regulated in main line 510 by a main pressure regulator valve518 shown in FIG. 2a, the valve delivering the excess fluid to lubricateparts of the power train. The main pressure regulator valve 518 has aregulator valve element 520 having lands a and b of equal diameterlocated in bore 522 of the valve body. Regulator valve element 520 isnormally biased to the right to the position shown by two springs 524and 526. The spring 524 is located between left end wall 527 of thevalve body and a shoulder 530 on the regulator valve element 520. Thespring 526 is located in a blind bore 532 in the left end of theregulator valve element 520 and between the regulator valve element anda plug 536 which is bottomed at its left end on the valve body wall 527,the regulator valve element being movable with respect to plug 536. Themain line 510 is always connected to the bore 522 in the space betweenlands a and b. This space is always connected to a passage 538 inregulator valve element 520 having a springloaded ball check valve 540therein permitting fluid flow from the main line 510 to the bore 522between land b and right end wall 542 of the valve body. The fluidadmitted to the right end of the valve bore 522 acts on the exposed endarea of land b so that the valve regulates the pressure in main line 510with the normal action of the regulating springs 524 and 526. The checkvalve 540 in cooperation with an orifice 544 through land b damps theaction of the regulator valve. The fluid overage resulting from theregulating action upon leftward regulator valve element movement tomaintain the main line pressure is delivered to a lubrication line 546.

The action of regulating springs 524 and 526 with no assist establishesa low main pressure in main line 510. This low main pressure is usedwhen the control system is controlling third and fourth drive rangeoperations in either forward or reverse and neutral. When the powertrain is operating in the first and second drive ranges in eitherforward or reverse, the regulating springs are assisted by fluidpressure to boost main line pressure to a higher regulated value, Theregulated high main pressure is provided by directing a signal pressureindicating first and second drive range operation to a port 548 in thevalve body which is continuously connected by a channel 550 in land a ofthe regulator valve element 520 and a passage 552 to chamber 554 in theleft end of the regulator valve element, such chamber being provided bythe bore 532 and plug 536. The fluid pressure thus delivered to thechamber 554 acts leftward on the bottomed plug 536 and rightward on theregulator valve element 520 thereby assisting the regulating springs andboosting the regulated pressure in main line 510 to the higher value.

The main pressure, when it is at either its low or high value, isdecreased during converter lockup operation. This is permissible sincelower torque at higher rotating speeds is being transmitted through thepower train. To this end, the regulator valve element 520 has a reduceddiameter portion 556 which extends through an aperture in the end wall542 of the valve body into a chamber 558. When fluid pressure indicatinglockup operation is delivered to the chamber 558 as described in moredetail later, such pressure acts leftward on the regulator valve element520 to decrease main line pressure.

The main line 510 is connected to the damping chamber 430 of thehydrostatic supercharge pressure regulator valve 416 and channel 462 ofthe converter pressure regulator valve 442. Thus, fluid at the mainpressure is supplied to these valves for their operations as previouslydescribed.

FORWARD AND REVERSE MAIN PRESSURE REGULATOR VALVE Main line 510 is alsoconnected to a forward and reverse main pressure regulator valve 560which is shown in FIG. 2c. Valve 560 has a regulator valve element 561with lands a and b of equal diameter located in bore 562 of the valvebody. The valve element 561 is normally biased to the open positionshown by spring 564. A forward and reverse main line 566 is alwaysconnected to a passage 567 in the valve element having a springloadedball check valve 568 therein permitting fluid flow from the forward andreverse main line 566 to the right end of the valve bore 562. The fluidin the right end of the valve bore acts leftward on the full end area ofland b to close the connection to main line 510 so that the valveregulates the pressure in the forward and reverse main line 566 eventhough main pressure is subject to modulation which gives severalpressure levels as previously described. The check valve 568 incooperation with a small clearance between land b and the bore 562 dampsthe action ofthe regulator valve.

GOVERNORS The control system has two fluid velocity governors providingseparate speed governed pressures. These pressures are used to controldifferent operations in the control system.

One governor 569 called the G1 governor is shown in FIG, 2a and has anannular trough 570 connected to the power train shaft 242 which isdriven by the converter turbine 229. The annular trough 570 ismaintained suitably filled with fluid from the lubrication line 546 viaorifice 571 shown in FIG. 2c. This fluid impinges on the open end ofapivot tube 572 to provide in a G1 line 573 a governor pressure (GIpressure) which is proportional to converter turbine speed.

The other governor 574 called the G2 governor is also shown in FIG. 2aand has its annular trough 575 connected to the range unit output shaft280. The trough 575 is maintained suitably filled with fluid from thelubrication line 546 via orifice 571 like the G1 governor 569. Thisfluid impinges on either open end of a double ended pivot tube 576having a two-way check valve between the open ends to provide in a G2line 577 a governor pressure (G1 pressure) which is proportional tovehicle speed in second, third and fourth drive range operations inforward and reverse, the range unit output shaft 280 being stationary inthe first drive range in forward and reverse.

PRIMARY THROTTLE PRESSURE REGULATOR VALVE AND SECONDARY THROTTLEPRESSURE REGULATOR VALVE Three pressures indicating engine torque demandand used primarily for control of various automatic operations in thecontrol system are provided. These are T pressure, TV pressure and rangeTV pressure. The T and TV pressures are derived from forward and reversemain pressure in the line 566 by a primary throttle pressure regulatorvalve 580 (primary TV valve) and the range TV pressure is derived fromforward and reverse main pressure in line 566 by a secondary throttlepressure regulator valve 582 (secondary TV valve), both of these valvesbeing shown in FIG. 2c.

The primary TV valve 580 has a regulator valve element 584 having landsa and b of equal diameter located in a small diameter portion of a bore586 in the valve body. The valve also has a control valve element 587having lands a and b of equal diameter and larger in diameter than thelands of valve element 584 located in a large-diameter portion of bore586. A zero or closed throttle to full throttle regulating spring 589and a detent spring 590 of shorter length are located between the twovalve elements 584 and 587.

The positioning of the control valve element 587 is controlled by athrottle cam 591 which contacts the projecting right end of the controlvalve element 587 and is pivoted by pivot pin 592 on the valve body, thethrottle cam 591 being connected by suitable linkage to the enginethrottle control, not shown, which controls the throttling of the engine210. When the engine throttle is closed or at zero throttle position,the cam 591 is against a stop 593 and the two valve elements 584 and 587are positioned as shown with the outer spring 589 positioning thecontrol valve element 587 against the cam 591. At the zero (0) positionof the control valve element 587 which corresponds to closed enginethrottle, there is no spring loading on the regulator valve element 584and its land a blocks the forward and reverse main line 566 so that a TVline 594 receives no pressure, TV line 594 being continuously con nectedto the space between lands a and b of the regulator valve element. Asthe engine throttle is opened, the cam 591 is pivoted clockwise movingthe control valve element 587 leftward. This leftward movement causesthe spring 589 to load the regulator valve element 584 and opens theforward and reverse main line 566 so that fluid is delivered betweenlands a and b of the regulator valve element to the TV line 594. The TVline 594 is always connected to a passage 595 in the regulator valveelement 584 having a spring-loaded ball check valve 506 thereinpermitting fluid flow from the TV line 594 to chamber 597 at the leftend of the valve body. The fluid pressure in chamber 597 acts rightwardon the full end area of land a so that the valve regulates to provide TVpressure in the TV line 594 according to the acting spring bias ofregulating spring 589 with overage being delivered to an exhaust 598.The TV line 594 is also connected to the chamber 597 through an orifice600 so that the ball check valve 596 in cooperation with the orifice 600damps the regulating action of the valve. An exhaust 601 exhausts anyleakage that otherwise might collect in bore 586 between valve elements587 and 587. Since movement of the valve element 587 is proportional tothe engine throttle opening which is indicative of engine torque demand,the spring load thus provided on the regulator valve element 584 is alsoproportional to engine throttle opening and indicative of engine torquedemand. Thus, the TV pressure produced in TV line 594 is proportional toengine throttle opening and increases with increasing throttle openingand torque demand.

The control valve element 587 at a point corresponding to full enginethrottle opening and near the elements limit of leftward travel, 80percent for example, beings pressing the detent spring 590. Thus,leftward movement of control valve element 587 past 80 percent travelcauses the detent spring 590 to load the regulator valve element 584 inaddition to the spring bias of spring 589 while the linkage to theengine throttle passes through a detent. Thus, through detent past fullengine throttle, TV pressure increases rapidly at an increased rate toits maximum.

The TV line 594 is always connected at bore 586 around the control valveelement 587 and through the valve body as shown. The control valveelement 587 at a point about midway through its maximum travel, 40percent for example, connects the TV line 594 between the elements landa and b to a T line 604 and throughout the remainder of leftwardmovement of the control valve element. The TV pressure delivered to theT line 604 provides the T pressure which is thus the upper part of therange of TV pressure in TV line 594.

The secondary TV valve 582 has a regulator valve element 605 with equaldiameter lands a and b located in a bore 606 of the valve body. Aregulator spring 608 biases the regulator valve element 605 leftward toconnect the forward and reverse main line 566 via the space betweenlands a and b to a range TV line 610 which is always connected to thisspace. This space is always connected to a passage 612 in the regulatorvalve element having a spring-loaded ball check valve 614 thereinpermitting flow from the range TV line 610 to a chamber 616 at the leftend of the valve body. The fluid pressure in chamber 616 acts on thefull end area of land a to urge the regulator valve element 605rightward against the spring bias. With rightward. movement of regulatorvalve element 605, land a closes the connection to the forward andreverse main line 566 and opens the range TV line 610 between lands aand b to the TV line 594. The range TV line 610 is connected through anorifice 618 to chamber 616 so that the orilice and check valve 614cooperatively provide for damping regulator valve element movementduring pressure regulation. An orifice 619 exhausts any leakage thatmight otherwise collect in the right end of bore 606.

The secondary TV valve 582 regulates to provide minimum range TVpressure in range TV line 610 according to the bias of regulator spring608 as long as overage can exhaust the TV line 594, i.e., range TVpressure is greater than TV pressure.

When TV pressure is equal to or greater than the minimum range TVpressure determined by the regulator spring 608, overage exhaust isprevented by TV pressure. TV pressure is then transmitted from thelockup TV line 594 to the range TV line 610 by what was before theregulator exhaust connection of the secondary TV valve 582. The TVpressure in the range TV line 610 is transmitted to chamber 616 where itacts to hold the regulator valve element 605 in what would normally beits exhaust position so that the TV pressure connection is maintainedwhen TV pressure is equal to or greater than the a minimum range TVpressure.

Thus, the minimum range TV pressurein line 610 is provided by regulatingaction of the secondary TV valve 582. Higher range TV pressure in line610 is provided by TV pressure through the valve upon cessation of itsregulating action when TV pressure is equal to or greater than theminimum range TV pressure.

FLOW VALVE The main line 510 is connected to a range main line 626 by aflow valve 628 shown in F lG. 2a. Flow valve 628 has a valve element 630having lands a and b of equal diameter located in portion 632 of astepped bore 633 in the valve body and a land 0 of larger diameterlocated in bore portion 634. Main line 510 is connected to the left endof bore 633 to act rightward on the full end area of land a and isconnected to the range main line 626 via an orifice636 in the valvebody. The range main line 626 is connected via an orifice 638 to theright end of bore 633 where it acts leftward on the full end area of thelarger land 0.

When there is no flow from main line 510 to range main line 626throughorifice 636, the pressures on the opposite ends of the flow valveelement 630 are equal and the pressure on the larger land 0 holds thevalve in the no-flow position shown. In the no-flow position the valveelement 630 connects the G1 line 573 between lands a and b to aGl-lockup line 639 and b blocks a GLexhaust line 640 from the spacebetween lands a and b.

When there is flow, which occurs during a range shift, the pressure dropwhich results at the orifice 636 reduces pressure in the range main line626 and thus the pressure acting on the larger land 0. This pressurereduction is sufficient to cause the valve element 630 to move rightwardto a lockup cutoff or flow position. Rapid rightward movement of theflow valve element 630 is permitted by a ball check valve 641 whichunseats to permit flow from the right end of bore 633 to the range mainline 626. In the lockup cutoff position, land a of valve element 630blocks the G1 line 573 and the Gil-lockup line 639 is connected betweenlands a and b to the Gl-lockup line 640.

After the range shift is made, pressure increases in the range main line626 until the pressures at each side of the flow valve orifice 636 areagain equal. When this occurs, the check valve 641 closes and fluidflows back into the right end of bore 633 through the orifice 638 whichbypasses the check valve 641. The return flow through orifice 638 isslower than the flow through the check valve 641 and thus the leftwardmovement of the flow valve element 630 that results is slower than therightward movement. An exhaust 642 connected at the step in bore 630between lands b and c prevents hydraulic locking of valve element 630.

FLOW VALVE MODULATOR VALVE A flow valve modulator valve 646 shown inFlG. 2e provides for normal operation of the flow valve 628 to controlconnection of the Gl-lockup line 639 between the G1 line 573 and exhaustabove a predetermined part engine throttle opening on a range shift andbypasses the normal action of the flow valve 628 below this enginethrottle opening so that the G1 line 573 and Gl-lockup line 639 remainconnected on a range shift. The flow valve modulator valve 646 has avalve element 648 having lands a and [1 located in a bore 650 of thevalve body. The valve element 648 is biased upward by a spring 652 to abypass position connecting the G1 line 573 between lands a and b to theGl-exhaust line 640. Thus, when the flow valve 628 is in its lockupcutoff position and the flow valve modula' tor valve 646 is in itsbypass position, the G1 line 573 remains connected to the Gl-lockup line639.

The TV line 594 is connected to the upper end of bore 650 so that TVpressure acts downward on the full end area of land a of the valveelement 648 against the spring bias. The TV pressure above apredetermined part engine throttle opening prevails over the spring biasand moves the valve element 648 to the exhaust position shown c nnectingthe Gl-ex'naust line 640 between lands a and b to an exhaust 653 whileland a blocks the G1 line 573. Thus, when the flow valve 638 is in itslockup cutoff position and the flow valve modulator valve 646 is in itsexhaust position the Gl-lockup line 639 is disconnected from the G1 line573 and connected to exhaust 653.

LOCKUP VALVE A lockup valve 654 shown in FIG. controls the delivery ofmain pressure in main line 510 to a lockup clutch motor 656 shown inFIG. 2a which operates the converter lockup clutch 238. The lockup valve654 has a valve element 658 having lands a, b and c of equal diameterand a G1 plug 660 of larger diameter located in a stepped bore 662 inthe valve body. A spring 666 located in the left end of the bore urgesthe shift valve element 658 and the G1 plug 660 to the position shownwhich is the release position. In this position a lockup clutch line 668connected to both the lockup clutch motor 656 and the chamber 558 of themain pressure regulator valve 518 is exhausted between lands b and c toexhaust 670. Thus, the lockup clutch 238 is released and main pressureis regulated at its lower value by the main pressure regulator valve518. In addition, the lockup valve 654 when in the release positionconnects main line 510 between the lands a and b to a converter signalline 672 which is connected to chamber 456 of the converter pressureregulator valve 442. Thus, converter-in pressure is regulated at itshigh value by the converter pressure regulator valve 442 for normalconverter operation with the lockup clutch released.

The lockup valve element 658 is biased to the left to an apply or lockupposition by G1 pressure under the control of the flow valve 628 and theflow valve modulator valve 646. This is provided by connection of theGl-lockup line 639 to the bore 662 between the G1 governor plug 660 anda closure plug 673 which closes the right end of the bore. Thus, G1pressure acting leftward on the full end area of the G1 governor plug660 provides this bias only when the flow valve 628 is in its no-flowposition with no range shift occurring or in its lockup cutoff positionon the occurrence of a range shift but with modulator valve 646 in itsbypass position below the predetermined part engine throttle opening.When the flow valve 628 is in its lockup cutoff position with theoccurrence of a range shift and the flow valve modulator valve 646 is inits exhaust position below part engine throttle opening, the G1 pressureis exhausted from the lockup valve 654. An exhaust 671 preventshydraulic lock between plug 660 and valve element 658.

A controlled fluid pressure bias at the lockup valve 654 which assiststhe fixed bias of spring 666 in opposing the G1 pressure bias isnormally provided by the TV pressure and is assisted by the T pressurewhen the latter becomes available. When the lockup valve element 658 isin the release position shown, the TV line 594 is connected past land ato chamber 674 in the left end of the bore. The T line 604 is connectedby a ball check valve 676 to the chamber 674 and the chamber is alwaysconnected through an orifice 678 to an exhaust 680. The orifice 678maintains the pressure in chamber 674 when it is receiving fluid andrelieves the chamber of pressure when there is no supply. The checkvalve 676 prevents TV pressure from reaching the T line 604 during thetime when no T pressure exists which occurs during zero and part enginethrottle opening (0-40 percent travel of the primary TV valve element587).

When converter turbine speed is sufficient to allow lockup clutchoperation, G1 pressure which is proportional to converter turbine speedis sufficient to move the lockup valve element 658 leftward to its applyposition. The TV pressure which is always available beyond closed enginethrottle admitted to chamber 674 past land a inhibits the initialleftward movement of the lockup valve. As the lockup valve element 658moves leftward, land a blocks delivery of TV pressure and the chamber674 is exhausted through orifice 678 to provide further leftwardmovement by snap action against the spring bias after TV pressure hasbeen overcome. Thus, when the lockup valve element 658 is in its applyposition and T pressure is not available, lockup clutch release isdelayed by requiring a lower G1 pressure (lower converter turbine speed)to enable the spring bias to move the lockup valve element to itsrelease position.

The T pressure which is provided by TV pressure only from 40 percentthrough percent travel of the primary TV valve element 587 is deliveredthrough the check valve 676 to chamber 674 of the lockup valve 654. Tpressure below its maximum value delays lockup clutch apply by requiringa higher G1 pressure (higher converter turbine speed) to move the lockupvalve element 658 to its apply position. T pressure at its maximum value(100 percent travel of the primary TV valve element 587 with enginethrottle open through detent) prevents movement of the lockup valveelement 658 to its apply position when it is in its release position andforces movement of the lockup valve element to its release position whenit is in its apply position.

The lockup valve 658 in its apply position connects the main line 510between lands b and c to the lockup clutch line 668 to engage the lockupclutch 238 and also to urge the main pressure regulator valve element520 leftward to allow more fluid to flow into the lubrication line 546,such added regulator valve bias effecting a reduction in main pressurewhich is permissible because lower torque at higher rotating speeds isbeing transmitted by the power train under these conditions. The lockupvalve 658 in its apply position also connects the converter signal line672 between lands a and b to an exhaust 682 so that the converterpressure regulator valve 442 regulates at the low value which ispossible since with the lockup clutch applied, there is no heat beinggenerated in the torque converter.

FORWARD AND REVERSE SHIFT VALVE The forward and reverse main line 566 inaddition to directing forward and reverse main pressure to the two TVvalves 580 and 582, also directs this pressure to a forward and reverseshift valve 684 shown in FIG. 2e. The forward and reverse shift valve684 is for connecting the forward and reverse main line 566 to either aforward clutch line 686 which delivers the pressure to a motor 688operating the forward drive clutch 246 or to a reverse clutch line 690which delivers the pressure to a motor 692 operating the reverse driveclutch 252. The forward and reverse shift valve 684 has a valve element694 having lands a, b, c and d of equal diameter located in a bore 696in the valve body. The shift valve element 694 is mechanically detentedby diametrically opposed spring loaded balls 698 which engage witheither one of a pair of concave surfaces between lands 0 and d to holdthe shift valve element in either its reverse clutch apply position asshown or its forward clutch apply position.

In the reverse clutch apply position the forward and reverse main line566 is connected between lands b and c to the reverse clutch line 690 toapply the reverse drive clutch 252. At the same time, the forward clutchline 686 is connected between lands a and b to the lubrication line 546which receives the overage from the main pressure regulator valve 518.The pressure in lubrication line 546 is regulated by a lubricationpressure regulator valve 700 shown in FIG. 2c which has a valve element702 normally biased to the closed position shown by a regulator spring704. Pressure in the lubrication line 546 is maintained by regulatingaction of valve 700 which opens against the spring bias to permit allfluid in excess of that required to maintain lubrication pressure andflow to return to the reservoir via exhaust 706. The regulatedlubrication pressure in the lubrication line 546 is low enough so thatthe fluid at this pressure fills the forward clutch motor 688 but doesnot effect forward clutch engagement to thus ready the disengagedforward drive clutch for subsequent engagement.

When the forward and reverse shift valve element 694 is moved to theright to the forward clutch apply position through the mechanicaldetent, the forward and reverse main line 566 is connected between landsa and b to the forward clutch line 246. The reverse clutch line 6'90 isthen connected between the lands b and c to the low pressure lubricationline 546 to release the reverse drive clutch 252 while the reverseclutch line 690 and reverse clutch motor 692 are maintained full offluid at the low lubrication pressure in readiness for subsequentreverse drive clutch engagement.

The positioning of the forward and reverse shift valve element 694 iscontrolled by fluid pressure bias. The valve bore 696 is closed at bothends providing chambers 710 and 712 at the opposite ends of the valveelement 694. Chambers 710 and 712 are simultaneously supplied with fluidfrom the forward and reverse main line 566 via orifices 713 and 714,respectively, as subsequently described and their closure and exhaust isselectively provided by solenoid valves 715 and 716, respectively. Thechambers 710 and 712 are connected to control lines 718 and 720,respectively, and both of the solenoid valves 715 and 716 are normallydeenergized in which condition they are closed and block the controllines 718 and 720 from exhausts 722 and 723, respectively, to thus closethe chambers. The chambers 710 and 712 when supplied from the forwardand reverse main line 566 then have full forward and reverse mainpressure which acts on the full end area of lands a and d and thus thereis a fluid pressure balance on the valve element 694 and the mechanicaldetent 698 holds the valve in one of its two positions. The solenoidvalves 715 and 716 have internal orifices larger than the orifices 713and 714 and upon energization of one of the solenoid valves it will beopened and exhaust one chamber of pressure through its internal orificepermitting the retained pressure on the other end of the forward andreverse shift valve element 694 to move the valve through the mechanicaldetent into the other detented position. With the forward and reverseshift valve 684 in the reverse clutch apply position shown, energizationof the solenoid valve 716 exhausts chamber 712 of pressure permittingthe retained pressure acting in chamber 710 to move the valve rightwardthrough the detent to the forward clutch apply position. Alternatively,energization of the solenoid valve 715 exhausts chamber 710 permittingthe retained pressure in chamber 712 to move the valve leftward to thereverse clutch apply position.

FORWARD AND REVERSE SHIFT INHIBITOR VALVE A forward and reverse shiftinhibitor valve 724 shown in FIG. 2:: permits the forward and reverseshift valve 684 to shift the power train between forward and reverse inthe first drive range and prevents shifting between forward and reversein all higher drive ranges. The forward and reverse shift inhibitorvalve 724 has a valve element 726 with lands a and b of equal diameterlocated in a bore 728 in the valve body. The valve 724 further has a G2plug 730 and a stop plug 732 both of the same diameter as lands a and blocated in the bore 728. A spring 734 normally biases the valve membersleftward to the position shown with plug 732 acting as a stop. In thisposition which is the forward-reverse shift permit position the forwardand reverse main line 566 is connected through the valve 724 between itslands a and b and then through the orifices'7l3 and 714 to therespective chambers 710 and 712 of the forward and reverse shift valve684. Thus, with the forward and reverse shift inhibitor valve 724 in itsforward-reverse shift permit position, the forward and reverse shiftvalve 684 may be operated by its solenoid valves 715 and 716 toselectively apply the forward drive clutch 246 and the reverse clutch252.

Forward-reverse shift prevention is provided by connecting the G2 line577 to deliver G2 pressure to a chamber 736 where it acts on the fullleft end area of the G2 plug 730 to urge the G2 plug and valve element726 rightward against the spring bias to an inhibit position in whichland a of the valve element blocks the forward and reverse main line 566at the upstream side of the valve and connects the forward and reversemain line 566 at the downstream side to an exhaust 740. With bothchambers 710 and 712 of the forward and reverse shift valve 684 thusexhausted by the forward and reverse shift inhibitor valve 724,operation of the solenoid valves 715 and 716 is ineffective to shift theforward and reverse shift valve 684 from the position it then occupieswhich will either be forward or reverse. Since G2 pressure isproportional to the range unit output speed which is zero throughout thefirst drive range, no G2 pressure is delivered to the forward andreverse shift inhibitor valve 684 during first drive range operation ineither forward or reverse and thus the forward and reverse shiftinhibitor valve will be in its permit position as shown to permit theoperator to shift the power train between forward and reverse in thefirst drive range. Exhausts 740, 742 and 744 are provided to preventhydraulic lock in the forward and reverse shift inhibitor valve 724.

When the vehicle is moving in either the forward or reverse direction ineither the second, third or fourth drive range the G2 pressure is alwayspresent and conditions the forward and reverse shift inhibitor valve 724in its inhibit position to prevent the forward and reverse shift valve684 from effecting shifts between forward and reverse. Thus, theoperator is prevented from making a shift between forward and reverse inthe second, third and fourth drive range which might overload the powertrain, shifts between forward and reverse in the first drive range beingpermitted for rocking the vehicle in low traction situations.

SEQUENCE VALVE A sequence valve 746 shown in FIG. 22 is for disengagingthe low low brake 318 during shifts between the first forward and firstreverse drive range to permit engagement of the directional clutches(clutches 246 and 252) under no load conditions recalling thatdirectional changes are prevented in the second, third and fourth driverange in forward and reverse by the forward and reverse shift inhibitorvalve 724. The sequence valve 746 has a valve element 748 having lands aand b of equal diameter and a plug 750 of the same diameter located in abore 752 in the valve body. The valve elements 748 and 750 are biasedrightward by a spring 754 to the position shown which is the releaseposition. In the release position, a 1-2 line 756 which normallyconnects the range line 626 to engage the low low brake 318 as describedin more detail. later is connected between the lands a and b of valveelement 748 to an exhaust 758 to release the low low brake 318.

The forward clutch line 686 and reverse clutch line 690 from the forwardand reverse shift valve 684 are continuously connected to the bore 752of the sequence valve 746 at the right end of plug 750 and between valveelement 748 and plug 750, respectively. Thus, when the reverse driveclutch 252 is engaged with the forward and reverse shift valve 684 inthe reverse clutch apply position shown, forward and reverse mainpressure acts on both the full right end area of land b of the valveelement 748 and the full left end area of plug 750 while the lowerlubrication pressure acts on the full right end area of valve plug 750.The fluid pressure imbalance on plug 750 holds it in the position shownand the fluid pressure on valve element 748 moves it leftward againstthe spring bias to a normal apply position. In the normal applyposition, land b of valve element 748 blocks exhaust 758 and the 1-2line 756 is connected through the valve between lands a and b for mainpressure transmittal to engage the low low brake 318. When the forwardand reverse shift valve 684 is operated to change vehicle direction fromreverse to forward in the first drive range which normally has the lowlow brake 318 engaged, the forward clutch line 686 is supplied withfluid from the forward and reverse main line 566 which fluid is alsoadmitted to act on the right end of plug 750 while the reverse clutchline 690 is filled with lubrication fluid which is also admitted to acton the right end of land b and on the left end of plug 750. As theforward clutch 246 is engaged and with the leftward acting fluidpressure on the valve element 748 thus reduced to the low lubricationpressure, the leftward acting pressure on plug 750 is below the normalforward and reverse main pressure because of the flow requirements forthe clutch engagement. This permits the spring 754 to move the valveelement 748 rightward to its release position against plug 750 whichremains to the right so that while the forward drive clutch 246 is beingengaged, the 12 line 756 is exhausted through exhaust 758 to drop out orrelease the low low brake 318. The pressure in the forward clutch line686 rises with engagement of the forward drive clutch until full forwardand reverse main pressure is reached. Full forward and reverse mainpressure or a slightly lower pressure is effective to move plug 750 andthe contacting valve element 748 leftward to reestablish connection ofthe 1-2 line 756 through the valve and thus reestablish engagement ofthe low low brake 318.

When the forward and reverse shift valve 684 is operated to changevehicle direction from forward to reverse in the first drive range, thefluid from the forward and reverse main line 566 is admitted to act onthe right end of land b of valve element 748 and the left end of plug750 while lubrication fluid is admitted to act on the right end of plug750. As the reverse drive clutch 252 is engaged and with the leftwardacting pressure on the plug 750 thus reduced to the low lubricationpressure, the fluid pressure acting leftward on the valve element 748and rightward on the plug 750 is below the normal forward and reversemain pressure because of the flow requirements for the clutchengagement. This permits the spring 754 to move the valve element 748and contacting plug 750 rightward to the release position so that whilethe reverse drive clutch 252 is being engaged, the low low brake 318 isreleased. The pressure in the reverse clutch line 690 rises withengagement of the reverse drive clutch until full forward and reversemain pressure is reached. Full forward and reverse main pressure or aslightly lower pressure is effective to move valve element 748 leftwardto its apply position to reestablish engagement of the low low brake 318while the plug 750 is held to the right by its pressure imbalance.

NEUTRAL SHIFT VALVE A neutral shift valve 759 shown in FIG, 2b is forconditioning the power train in neutral and has a valve element 760having lands a and b of equal diameter located in a bore 762 in thevalve body, A spring 764 urges the valve element 760 forward the neutralposition shown in which land a blocks the range main line 626 upstreamof the valve and connects the range main line downstream of the valvebetween the lands a and b to an exhaust 768. The forward and reversemain line 566 is connected through an orifice 770 to a chamber 772 atthe right end of the valve element 760. A solenoid valve 774 isconnected by a control line 776 to the chamber 772 and when deenergizedblocks the line 776 and thus chamber 772 from an exhaust 778. When thechamber 772 is thus blocked, the chamber is filled through orifice 770and the pressure rises to full forward and reverse main pressure. Thispressure acts on the full end area of land b and is effective to movethe valve element 760 leftward to a range shift position. The valveelement 760 in the range shift position connects the range main line 626through the valve between lands a and b while land b blocks exhaust 768,an exhaust 779 preventing hydraulic lock in the valve.

When the solenoid valve 774 is energized it connects the chamber 772 viathe line 776 to the exhaust 778 through an internal orifice larger thanorifice 770 to prevent pressure buildup in the chamber which is beingcontinuously fed through orifice 770. This pressure exhaust permits thespring 764 to move the valve element 760 to its neutral positionblocking the range main line 626 at the upstream side and exhausting thedownstream range main line.

MANUAL SIGNAL VALVE A manual signal valve 780 shown in FIG. 2b providesselective delivery of forward and reverse main pressure for manuallycontrolled shifts to all the drive ranges below the highest (1, 2 and 3)and T pressure for all automatic shifts. The manual signal valve 780 hasa valve element 782 having lands a, b and c of equal diameter located inportion 784 of a stepped bore 785 in the valve body and a land d ofsmaller diameter located in bore portion 788. A spring 790 biases thevalve element 782 rightward toward the manual signal position shown, Inthis position, the T line 604 is blocked at the upstream side of thevalve by land a and is connected at the downstream side of the valvebetween the lands a and b to an exhaust 789. In addition, the forwardand reverse main line 566 is connected in the manual signal positionthrough the manual signal valve between lands b and c.

The forward and reverse main line 566 upstream of the manual signalvalve 780 is always connected through an orifice 792 to a chamber 794 atthe step in bore 785, the effective right end area of land 0 of valveelement 782 (land c minus land d) always being exposed to this chamber.The chamber 794 downstream of orifice 792 is connected by line 566 to asolenoid valve 798. The solenoid valve 798 when deenergized blocks thechamber 794 from an exhaust 800 so that pressure builds in the blockedchamber to full forward and reverse main pressure. When the solenoidvalve 798 is energized it connects chamber 794 to the exhaust 800through an internal orifice larger than orifice 792 to prevent pressurebuildup in this chamber.

The forward and reverse main line 566 upstream of the manual signalvalve 780 is also always connected through an orifice 801 to a chamber802 in the right end of bore 785, the full right end area of land 11 ofvalve element 782 being exposed to this chamber. The chamber 802downstream of orifree 801 is connected by line 566 to a solenoid valve803. The solenoid valve 803 when deenergized blocks the chamber 802 froman exhaust 804 so that pressure builds in the blocked chamber to fullforward and reverse main pressure. When the solenoid valve 803 isenergized it connects chamber 802 to the exhaust 804 through an internalorifice larger than orifice 801 to prevent pressure buildup in thischamber.

The fluid pressure force required to overcome the force of spring 790 tomove valve element 782 leftward to an automatic signal position isprovided only when full forward and reverse main pressure is present inboth chambers 794 an 802, i.e., only when both solenoid valve 798 and803 are deenergized. In the automatic signal position, the T line 604 isconnected through the manual signal valve 780 between its lands a and band the forward and reverse main line 566 downstream of this valve isconnected between lands b and c to exhaust 789 while this line at theupstream side of this valve is blocked by land 0.

AUTOMATIC SHIFT INHIBITOR VALVE An automatic shift inhibitor valve 806shown in FIG. 2c is for inhibiting automatic range shifting duringsteering operation. This valve has a valve element 808 having lands a, band c of equal diameter and a valve element or plug 810 of the samediameter all located in a bore 812 in the valve body. A spring 814normally biases the valve elements 808 and 810 to the position shownwhich is an automatic shift permit position. In this position, the Tline 604 is connected to the manual signal valve 780 through theautomatic shift inhibitor valve 806 between lands a and b and the rangeTV line 610 is connected through the automatic shift inhibitor valvebetween lands b and 0 while the forward and reverse main line 566 whichis continuously connected through the valve body of the secondary TVvalve 582 as shown is blocked at the automatic shift inhibitor valve byits land 12.

A chamber 816 at the right end of the valve bore 812 is connected toreceive a signal pressure indicating steering operation from thehydrostatic steer control portion of the system later described. Whenthe steer signal pressure is provided, it acts on the full right endarea of plug 810 to move it and the contacting valve element 808leftward to a shift inhibit position. In this position, the T line 604which is connected to the manual signal valve 780 downstream of theautomatic shift inhibitor valve 806 is connected between lands a and bto an exhaust 818 and the forward and reverse main line 566 is connectedbetween lands b and c to the range TV line 610 downstream of theautomatic shift inhibitor valve while the range TV line 610 at theupstream side is blocked by land 0.

Thus, provided there is no steering operation occurring, the T and rangeTV pressures are made available by the automatic shift inhibitor valve806 to control range shifting as later described. When steeringoperation occurs in any range during automatic operation, the downstreamT pressure is exhausted by the automatic shift inhibitor valve 806 whichthen delivers forward and reverse main pressure instead of range TVpressure to range TV line 610 downstream of this valve for inhibitingautomatic shifting during steering.

1-2 RANGE SHIFT VALVE A 1-2 range shift valve 820 shown in FIG. 2bcontrols the engagement of both the low low brake 318 and the low brake271 to establish the first and second drive range, respectively. The 1-2rangeshift valve 820 has a shift valve element 821 having lands a, b,cand d located in a steppedbore 822 in the valve body. The shift valveelement is biased rightward toward a downshift position as shownby aspring 824 acting through a contacting downshift plunger 826 having aland located in the left end of bore 822. In the downshift position, the1-2 line 756 downstream of the sequence valve 746 is connected betweenlands b and c of shift valve element 821 to a low low brake line 827that is connected to a motor 828 shown in FIG. 2a which operates the lowlow brake 318. The 1-2,range shift valve in the down shift position alsoconnects an exhaust 829 between lands 0 and d to a low brake line 830,this line being connected to a motor 831 shown in FIG. 2a which operatesthe low brake 271. Thus, with the 1-2 range shift valve in its downshiftposition, the low low brake 318 is engaged provided the 12 line 756 issupplied with pressure and the low brake 271 is disengaged to producethe first drive range.

The 1-2 range shift valve 820 further has a plug or valve element 832having a land a and a larger land b located in the right end of bore822. The left end of land a of the plug 832 contacts the right end ofvalve element 821 and the G1 line 573 whose G1 pressure is used toprovide an upshift control pressure is connected to the bore 822 betweenland a and b of the plug 832 in the downshift position and is alwaysconnected to the closed right end of bore 822. G1 pressure acts on theunbalanced area of land b of the plug 832 to urge movement of the valveelement 821 leftward towards its upshift position. This upshiftconverter turbine speed governed bias is resisted by; the constant biasof spring 824 and a controlled-pressure downshift bias which is providedby range TV pressure in the downshift position and by T pressure in theupshift position when the latter pressure becomes available. Thisdownshift control pressure bias is effected by connection of the rangeTV line 620 downstream of the automatic shift inhibitor valve 806 to thebore 822 between land a of the downshift plunger 826 and land a of thevalve element 821 only when the 1-2 range shift valve is in itsdownshift position and continuous connection of the T line 604downstream of the-manualsignal valve 780 through a ball check valve 838to this same location which is always connected through an orifice 840to an exhaust 842. Land a of valve element 821 is larger in diameterthan land a of the downshift plunger 826 so that there is an unbalancedpressure area to provide the rightward downshift throttle pressureforce. The orifice 840 maintains the downshift pressure bias as long asthereis fluid supply. The check valve 838 prevents range TV pressurefrom reaching the T line 604 when no T pressure exists.

During automatic operation, upshifting occurs when the G1 pressureacting leftward on the unbalanced area of plug 832 is greater than thedownshift bias of the spring 824 and the range TV pressure actingrightward on the unbalanced area of land a of valve element 821. Duringinitial leftward upshift movement of the plug 832 the space between itslands a and b is connected to anexhaust 844 while land b closes thisspace to the G1 line 573 so that the full end area of land b iseffectively acted on by G1 pressure to accelerate leftward upshift valvemovement. In the upshift position land a of the valve element 821 blocksthe range TV line 610 from bore 822 so that the range TV pressurepreviously acting on the unbalanced area of this land is relievedthrough orifice 840 to exhaust 842. In the upshift position, the low lowbrake line 827 is connected between lands b and c of valve element 821to an exhaust 846 to release the low low brake 318 while the 1-2 line756 downstream of the sequence valve 746 is connected between lands cand d of valve element 821 to the low brake. line 830 to engage the lowbrake 271 to establish the second drive range.

When vehicle speed reduces sufficiently for the bias providedby spring824 to overcome the G1 pressure force, the 1-2 range shift valve 820downshifts. As the shift valve element 821 moves rightward towards itsdownshift position, range TV pressure is restored to act on theunbalanced end area of land a. of valve element 821. Downshifting isaccelerated or made to occur earlier than the fixed downshift conditiondescribed above when there is large torque demand. This is provided bythe use of T pressure from the T line 604 downstream of the manualsignal valve 780: The T pressure acts on the left end area of land a ofthe valve element 821 to provide a downshift bias which is greater thanthe bias of spring 824 and increases with torque demand. Thus, above the40 percent travel in the primary TV valve 581 where only then T pressureis made available and where large torque demand is being experienced, a2-1 downshift is made to occur earlier than it normally would withoutthe added T pressure bias. Exhausts 834, 835 and 836 are connected tobore 822 as shown to prevent hydraulic lock.

A hysteresis effect provides for snap action of the 1-2 range shiftvalve to its upshift and downshift position to prevent partial orvibratory valve movement. For this purpose the lands of valve element821 are sized so that land a is slightly larger in diameter than land b,land b is equal in diameter to land c, and land c isslightly larger indiameter than land d, the valve bore 822 being stepped accordingly. Whenthe shift valve element 821 is in its downshift position as shown, thereis no hysteresis force provided and as it is moved leftward towards itsupshift position a hysteresis chamber 84 between lands a and b of thevalve element is opened to the forward andreverse main line 566 whileland b moves to block an exhaust 850 which serves to exhaust thischamber on downshifting. .The forward and reverse main pressure thusadmitted to the hysteresis chamber 848 acts on the unbalanced area ofland a of valve element 821 to provide an unbalanced force snapping thevalve element leftward to its upshift position. In the upshift positionthe main pressure transmitted between lands 0 and d for the second driverange establishment acts leftward on the unbalanced area of land c toaid in holding the valve element 821 in its upshift position. Whendownshift movement occurs, the unbalanced hysteresis force on land c isfirst relieved through exhaust 829 and the the pressure in hysteresischamber 848 is relieved through exhaust 850 to provide snap action inthe rightward movement of the valve element 821 to its downshiftposition.

The supply of fluid at G1 pressure is supplemented by a G1 accumulator852 shown in FIG. 2b. This is to ensure that ,upshiftmovement of thel-,-2v range shift valve after it has been initiated is maintained bythe G1 pressure which signaled for the shift, i.e., prevent a pressuredrop in G1 pressure during the shift because of the increasing volumeand since G1 prescharged with a volume of fluid at G1 pressure. Thus,when fluid at G1 pressure from the G1 line 573 is used to move the 1-2range shift valve towards its upshift position, the G1 accumulator 852supplements the main fluid supply to help maintain G1 pressure at the1-2 range shift valve for the upshift with orifice 860 helping tomaintain G1 pressure upstream of the 1-2 range shift valve. The lowbrake line 830 is connected to the closed right end of bore 856 of theG1 accumulator valve 852 so that it adds to the bias of spring 858 toboost the accumulator valve action during the upshift.

Control of the 1-2 range shift valve 820 for manual selection of thefirst drive range from a higher range is provided by a piston 861located in a bore 862 in the valve body and contactable with the leftend of downshift plunger 826. The bore 862 at the left end or head ofpiston 861 is connected to the forward and reverse main line 566downstream of the manual signal valve 780. Thus, when the solenoid valve798 is energized to condition the manual signal valve 780 in its manualsignal position, the T pressure downshift bias, if it was available, onthe l-2 range shift valve is relieved and the forward and reverse mainpressure acts rightward on the piston 861 to apply a constant downshiftbias to the plunger 826 and thus the valve element 821 and plug 832 inaddition to the constant downshift bias of spring 824. The constanttotal downshift bias thus provided for manual selection of the firstdrive range is determined so that a 2-1 downshift will occur only belowa predetermined G1 pressure to prevent first drive range establishmentat vehicle speeds that would be excessive for this drive range.

Manual control of the 1-2 range shift valve 820 for manual selection ofthe second drive range is provided by a plunger 863 which is located ina bore 864 of the valve body and has a projection 865 extending throughwall 866 to contact the right end of plug 832. Plunger 863 is urgedleftward by a spring 867. A chamber 868 provided by bore 864 to the leftof plunger 863 is continuously connected to the forward and reverse mainline 566 downstream of orifice 801 and is continuously connected to thesolenoid valve 803 downstream of orifice 801 like chamber 802 of themanual signal valve 780.

The solenoid valve 803 when deenergized blocks the chamber 868 fromexhaust 804 so that pressure builds in chamber 868 to full forward andreverse main pressure which is effective to hold plunger 863 in theposition shown against the bias of spring 867. In this position theplunger 863 acts as a stop for the plug 832 and has no other effect topermit automatic operation of the l-2 range shift valve.

When the solenoid valve 803 is energized it acts to relieve chamber 868of pressure through exhaust 804. This permits the spring 867 to apply aconstant upshift bias through plunger 863 to the plug 832 and thus valveelement 821 in addition to the G1 pressure upshift bias. Thus, when thesolenoid valve 803 is energized to condition the manual signal valve 780in its manual signal position, the constant total downshift bias isprovided as previously described with the solenoid valve 798 energizedbut now this downshift bias is opposed by the added constant upshiftbias. The total upshift bias thus provided for manual selection of thesecond drive range is determined so that a l2 upshift will occurimmediately and throughout the G1 pressure range in the first driverange including when the vehicle is stationary with G1 pressure at zero.

23 RANGE SHIFT VALVE A 23 range shift valve 870 shown in FIG. 2bcontrols the engagement of the intermediate clutch 276 to establish thethird drive range and also selectively permits and preventsestablishment of the first and second drive range. The 2-3 range shiftvalve 870 has a valve element 872 having lands a, b, c and d located ina stepped bore 874 in the valve body. The valve element 872 is biasedrightward toward a downshift position as shown by a spring 876 actingthrough a contacting downshift plunger 878 having a land located in theleft end of bore 874. In the downshift position, the range main line 626downstream of the neutral shift valve 759 is connected between lands band c of valve element 872 to the 12 line 756 at the latter line's pointof origination. The 2-3 range shift valve in the downshift position alsoconnects an exhaust 880 between lands c and d to an intermediate brakeline 882, this line being connected to a motor 884 shown in FIG. 2awhich operates the intermediate brake 276. Thus, when the 2-3 rangeshift valve 870 is in its downshift position, the intermediate brake 276is disengaged and fluid in the range main line 626 is permitted to passto the I-2 line 756 for delivery to the l-2 range shift valve 820 forestablishment of the first and second drive range.

The 2-3 range shift valve 870 also has a plug or valve element 885located in the right end of bore 874. The left end of plug 885 contactsthe right end of valve element 872 and the G2 line 577 whose G2 pressureis used to provide an upshift control pressure is connected to theclosed right end of bore 874. G2 pressure acts on the full right endarea of plug 885 to urge movement of the valve element 872 leftwardtowards its upshift position. This upshift output speed governed bias isresisted by the constant bias of spring 876 and a controlled pressuredownshift bias which is provided by range TV pressure in the downshiftposition and by T pressure in the upshift position when the latterpressure becomes available. This downshift control pressure bias iseffected by connection of the range TV line 610 downstream of theautomatic shift inhibitor valve 806 to the bore 874 between land a ofthe downshift plunger 878 and land a of the valve element 872 only whenthe 2-3 range shift valve is in its downshift position and continuousconnection of the T line 604 downstream of the manual signal valve 780through a ball check valve 886 to this same location which is alwaysconnected through an orifice 887 to an exhaust 888. Land a of valveelement 872 is larger in diameter than land a of the downshift plunger878 so that there is an unbalanced pressure area to provide therightward downshift throttle pressure force. The orifice 887 maintainsthe downshift pressure bias as long as there is fluid supply and thecheck valve 886 prevents range TV pressure from reaching the T line 604when no T pressure exists.

During automatic operation, upshifting occurs when G2 pressure actingleftward on plug 885 is greater than the downshift bias of the spring 86and the range TV pressure acting rightward on the unbalanced area ofland a of valve element 872. In the upshift position, land a of valveelement 872 blocks the range TV line 610 from bore 874 so that the rangeTV pressure previously acting on the unbalanced area of this land isrelieved through orifice 887 to exhaust 888. In the upshift position,the 12 line 756 is disconnected from the range main line 626 andconnected between lands b and c to exhaust 889 to release the low brake271 with the range main line 626 then being connected between lands 0and d to the intermediate brake line 882 to engage the intermediatebrake 276 to establish the third drive range with land d blockingexhaust 880.

When vehicle speed reduces sufiiciently for the bias provided by spring876 to overcome the G2 pressure force, the 2-3 range shift valve 870downshifts to establish the second drive range. Downshifting isaccelerated or made to occur earlier than the fixed downshiftingdescribed above when there is large torque demand. This is provided bythe use of T pressure from the T line 604 downstream of the manualsignal valve 780. The T pressure acts on the unbalanced left end area ofland a of valve element 872 to assist the spring 876 and provide adownshift bias which then increases with torque demand. Thus, above the40 percent travel in the primary TV valve 580 where only then T pressureis made available and where large torque demand is being experienced, a3-2 downshift is made to occur earlier than it normally would withoutthe T pressure bias. The intermediate brake line 882 is connectedthrough an orifice 890 to a chamber 891 behind upshift plunger 863 ofthe 1-2 range shift valve 820 so that when the 2-3 range shift valve 870is in its upshift position establishing the third drive range, mainpressure is also in chamber 891 to permit the spring 867 to aid G1pressure in holding the 1-2 range shift valve 820 in its upshiftposition for a 3-2 downshift. Exhausts 893, 894 and 895 are connected tobore 874 as shown to prevent hydraulic lock.

A hysteresis effect is provided for snap action of the 2-3 range shiftvalve 870 to its upshift and downshift position to prevent partial orvibratory valve movement. For this purpose, the lands of valve element872 are sized so that land a is slightly larger in diameter than land b,land 12 is equal in diameter to land c and land is slightly larger indiameter than land d, the valve bore 874 being stepped accordingly. Whenthe valve element 872 is in its downshift position as shown, there is nohysteresis force provided and as it is moved leftward towards itsupshift position, a hysteresis chamber 896 between lands a and b of thevalve element is opened to the forward and reverse main line 566 whileland b moves to block an exhaust 898 which serves to exhaust thischamber on downshifting. The forward and reverse main pressure thusadmitted to the hysteresis chamber 896 acts on the unbalanced area ofland a of valve element 87 to provide an imbalance snapping the valveelement leftward to its upshift position. In the upshift position, themain pressure transmitted between lands c and d for the second driverange establishment acts leftward on the unbalanced area of land c toaid the holding valve element 872 in its upshift position. Whendownshift movement occurs, the unbalanced hysteresis force on land c isfirst relieved through exhaust 880 and then the pressure in hysteresischamber 896 is relieved through exhaust 898 to provide snap action inthe rightward movement of valve element 872 to its downshift position.

To insure that upshift movement of the 2-3 range shift valve, after ithas been initiated, is maintained by the G2 pressure which signalled forthe shift, the supply of fluid at G2 pressure is supplemented by a G2accumulator 899 shown in FIG. 2b. The G2 accumulator 899 has a piston900 located in a bore 901 in the accumulator body which piston is urgedrightward by spring 902. The G2 line 577 is connected downstream of anorifice 903 to the closed right end of bore 901 so that G2 pressure actsto move piston 900 leftward against spring 902 to normally maintain theG2 accumulator charged with a volume of fluid at G2 pressure. Thus, whenfluid at G2 pressure from the G2 line 577 is used to move the 2-3 rangeshift valve towards the upshift position, the G2 accumulator 899supplements the fluid supply to help maintain G2 pressure at the 2-3range shift valve for the upshift with orifice 903 helping to maintainG2 pressure upstream of the 2-3 range shift valve. An exhaust 904connected to bore 901 behind the piston 900 prevents hydraulic lock inthe G2 accumulator.

Automatic downshift control of the 2-3 range shift valve 870 for manualrange selection is provided by a piston 906 located in a bore 907 in thevalve body and contactable with the left end of downshift plunger 878.The bore 907 at the left end or head of piston 906 is connected to theforward and reverse main line 566 downstream of the manual signal valve780. Thus, when the solenoid valve 798 is energized to condition themanual signal valve 780 in its manual signal position, the T pressuredownshift bias, if it was available to the 2-3 range shift valve, isrelieved and the forward and reverse main pressure acts rightward on thepiston 906 to apply a constant downshift bias to the plunger 878 andthus the valve element 872 and plug 885 in addition to the constantdownshift bias of spring 876. The constant total downshift bias thusprovided is determined so that a 3-2 downshift will occur only below apredetermined G2 pressure to prevent second drive range establishment atvehicle speeds that would be excessive for this drive range.

Manual control of the 2-3 range shift valve 870 for manual selection ofthe third drive range is provided by a plunger 908 which is located in abore 909 of the valve body and has a projection 910 extending throughwall 911 to contact the right end of plug 885. Plunger 908 is urgedleftward by springs 912. A chamber 914 provided by here 909 to the leftof plunger 908 is continuously connected to the forward and reverse mainline 566 downstream of an orifice 916 and is continuously connecteddownstream of this orifice to a solenoid valve 918. The solenoid valve918 when deenergized blocks the chamber 914 from an exhaust 919 so thatpressure builds in the blocked chamber to full forward and reverse mainpressure which is effective to hold plunger 908 in the position shownagainst the bias of springs 912. In this position the plunger 908 actsas a stop for plug 885 and has no other effect to permit automaticoperation of the 2-3 range shift valve.

When the solenoid valve 918 is energized, it connects the chamber 914 tothe exhaust 919 through an internal orifice larger than orifice 916 toprevent pressure buildup in this chamber. This permits the springs 912to apply a constant upshift bias through plunger 908 to plug 885 andvalve element 872 in addition to the G2 pressure upshift bias. Thus,when the solenoid valve 798 is energized to condition the manual signalvalve 780 in its manual signal position, a constant total downshift biasis provided as previously described but now this downshift bias isopposed by the added constant upshift bias. The total upshift bias thusprovided for manual selection of the third drive range is determined sothat a 2-3 upshift will occur immediately and throughout the G2 pressurerange in the second drive range. Thus, if the operation prior to manualselection was lower than third, the shift to the third drive rangeimmediately takes place. An exhaust 920 connected to the bore 909 behindplunger 908 prevents hydraulic lock of the plunger.

3-4 RANGE SHIFT VALVE A 3-4 range shift valve 922 shown in FIG. 2bcontrols the engagement of the high clutch 278 to establish the fourthdrive range and also selectively permits. and prevents establishment ofall the lower drive ranges, namely first, second and third drive range.The 3-4 rangeshift valve 922 has a valve element 924 having lands a, b,c and d located in a stepped bore 925 in the valve body. The valveelement 924 is biased rightward toward a downshift position as shown byspring 926 acting through a contacting downshift plunger 927 which has aland a located in the left end of bore 925. In the downshift position,the range main line 626 downstream of the neutral shift valve 759 isconnected through the 3-4 range shift valve between lands 1') and c ofvalve element 924 to the 2-3 range shift valve 870. The 3-4 range shiftvalve in the downshift position also connects an exhaust 928 betweenlands 0 and d to a high clutch line 929, this line being connected to amotor 930 shown in FIG. 2a which operates the high clutch 278. Thus,when the 3-4 range shift valve 922 is in its downshift position, thehigh clutch 278 is disengaged and fluid is permitted to pass through therange main line 626 to the 2-3 range shift valve 870 for establishmentof the first, second and third drive range.

The 3-4 range shift valve 922 also has a plug or valve element 931located in the right end of bore 925. The left end of plug 931 contactsthe right end of valve element 924 and the G2 line 577, whose G2pressure is used to provide an upshift control pressure, is connected tothe closed right end of bore 925. G2 pressure acts on the full right endarea of plug 931 which is smaller than the corresponding area of plug885 of the 2-3 range shift valve 870 to urge movement of the valveelement 924 leftward towards the upshift position. This upshift outputspeed governed bias is resisted by the constant bias of spring 926 and acontrolled pressure downshift bias which is provided by the range TVpressure in the downshift position and by the T pressure in the upshiftposition when the latter pressure becomes available. This downshiftcontrol pressure bias is effected by connection of the range TV line 610downstream of the automatic shift inhibitor valve 806 to the bore 925between land a of downshift plunger 927 and land a of valve element 924only when the 3-4 range shift valve is in its downshift position andcontinuous connection of the T line 604 downstream of he manual signalvalve 780

1. In a control system for a power train providing multiple drive rangesthe combination of range shift means for shifting drive ranges;automatic shift control means for controlling said range shift means toautomatically shift drive ranges in accordance with torque demand andoutput speed; and manual upshift-downshift control means including powersource means for selectively controlling said range shift means tomanually select the drive ranges by upshifting to selected higher speeddrive ranges and downshifting to selected lower speed drive ranges usingpower from said power source means and releasing control over said rangeshift means to said automatic shift control means on discontinuance ofpower from said power source means.
 2. The control system set forth inclaim 1 and said manual upshift-downshift control means includingautomatic downshift control means establishing constant downshift biaseson said range shift means and selective upshift control means providingselective upshift biases on said range shift means for controlling saidrange shift means to automatically downshift in accordance with onlyoutput speed to the manually selected lower drive range while providingfor immediate upshifts.
 3. In a control system for a power train thecombination of a plurality of fluid-pressure-operated drive-engagingmeans each operable on fluid pressure delivery thereto to establish adrive range; a fluid pressure source; primary throttle pressureregulator valve means operatively connected to said fluid pressuresource for providing a TV pressure increasing with increasing torquedemand and a T pressure equivalent to and derived from said TV pressureabove a predetermined intermediate TV pressure; secondary throttlepressure regulator valve means operatively connected to said fluidpressure source and said primary throttle pressure regulator valve meansfor providing a range TV pressure having a predetermined minimum valuegreater than zero and otherwise equivalent to and derived froM said TVpressure; first governor means for providing a G1 pressure increasingwith increasing output speed; second governor means for providing a G2pressure having a value of zero throughout the lowest drive range andincreasing with increasing output speed throughout the higher driveranges; shift valve means corresponding to each of said drive engagingmeans; said shift valve means operatively connected to theircorresponding drive engaging means and operatively connected in seriesto said fluid pressure source; the furthest downstream shift valve meansoperable in a downshift position to establish fluid pressure deliveryfrom said fluid pressure source to the drive-engaging means thatestablishes the lowest drive range and in an upshift position to exhaustfluid pressure from the last-mentioned drive-engaging means whileestablishing delivery of the fluid pressure to the drive-engaging meansthat establishes the next higher drive range; each of the other of saidshift valve means operable in a downshift position to establish fluidpressure delivery from said fluid pressure source to the immediatedownstream shift valve means and in an upshift position to exhaust fluidpressure from the immediate downstream shift valve means whileestablishing delivery of the fluid pressure to the correspondingdrive-engaging means; means transmitting said G1 pressure to act on saidfurthest downstream shift valve means for providing an upshift biasbiasing said furthest downstream shift valve means to its upshiftposition; means transmitting said G2 pressure to act on all of the otherof said shift valve means for providing an upshift bias biasing each ofthe other of said shift valve means to its upshift position; meansnormally transmitting said range TV pressure to act on each of saidshift valve means only when each said shift valve means is in itsdownshift position for providing an upshift inhibitor bias opposing saidupshift bias on each said shift valve means; means normally transmittingsaid T pressure to act on each of said shift valve means for providing adownshift bias biasing each of said shift valve means to its downshiftposition; manually controlled signal valve means for preventing said Tpressure from acting on all of said shift valve means while transmittinga pressure derived from said fluid pressure source to act on all of saidshift valve means for providing a constant downshift bias biasing eachof said shift valve means to its downshift position and manuallycontrolled shift-controlling means corresponding to and operativelyconnected to each of said shift valve means for selectively providing anupshift bias on each of said corresponding shift valve means effectiveto immediately bias the corresponding shift valve means to its upshiftposition.
 4. The control system set forth in claim 3 and each saidmanually controlled shift-controlling means comprising electricallyoperated valve means operable in an energized condition to establish anupshift bias on the corresponding shift valve means greater than theopposing downshift bias and operable in a deenergized condition torelieve said last-mentioned upshift bias, an electrical power source,switch means for selectively connecting said electrical power source toeach said electrically operated valve means.
 5. In a control system fora power train the combination of a plurality of fluid-pressure-operateddrive-engaging means each operable on fluid pressure delivery thereto toestablish a drive range; a fluid pressure source; first governor meansdriven by the power train in at least one of the drive ranges forproviding a first governor pressure increasing with increasing outputspeed in at least said one drive range; second governor means driven bythe power train in all of the drive ranges except said one drive rangefor providing a second governor pressure increasing with increasingoutput in all of the drive ranges except said one drive range throttlepressure regulator valve means opEratively connected to said fluidpressure for providing a throttle pressure increasing with increasingtorque demand; shift valve means corresponding to each of saiddrive-engaging means; said shift valve means operatively connected totheir corresponding drive-engaging means and operatively connected inseries to said fluid pressure source; and one of said shift valve meansbeing responsive to said first governor pressure and said throttlepressure to upshift and downshift and each of the other of said shiftvalve means being responsive to said second governor pressure and saidthrottle pressure to upshift and downshift to provide sequentialdelivery of fluid pressure from said fluid pressure source to saiddrive-engaging means to automatically shift drive ranges.
 6. In acontrol system for a power train the combination of a plurality offluid-pressure-operated drive-engaging means each operable on fluidpressure delivery thereto to establish a drive range; a fluid pressuresource; shift means for selectively establishing fluid pressure deliveryfrom said fluid pressure source to said drive-engaging means to shiftdrive ranges; a pair of fluid-pressure-operated directionaldrive-engaging means each operable on fluid pressure delivery thereto toestablish a directional drive; forward and reverse shift valve meansoperable in a forward apply position to establish fluid pressuredelivery from said fluid pressure source to one of said directionaldrive-engaging means and in a reverse apply position to establish fluidpressure delivery from said fluid pressure source to the otherdirectional drive-engaging means; manually controlled directionaldrive-determining means for selectively moving said forward and reverseshift valve means between said forward and reverse apply positions,sequence valve means for relieving fluid pressure from thedrive-engaging means establishing the lowest drive range on movement ofsaid forward and reverse shift valve means between said forward andreverse apply positions, governor means for providing a governorpressure increasing with increasing output speed in all of the driveranges above said lowest drive range; forward and reverse shiftinhibitor valve means responsive to said governor pressure forpreventing said forward and reverse shift valve means from shiftingbetween said forward and reverse apply positions in all of the driveranges above said lowest drive range.
 7. In a control system for a powertrain providing multiple drive ranges in both forward and reverse thecombination of range shift means for shifting drive ranges; automaticshift control means for controlling said range shift means toautomatically shift drive ranges in accordance with torque demand andoutput speed; manual shift control means including power source meansfor controlling said range shift means to manually select the driveranges using power from said power source means and releasing controlover said range shift means to said automatic shift control means ondiscontinuance of power from said power source means; directional shiftmeans for shifting between forward and reverse; and forward and reverseshift inhibitor means for preventing said directional shift means fromshifting between forward and reverse in at least the highest driverange.
 8. In a control system for a power train providing multiple driveranges in both forward and reverse the combination of range shift meansfor shifting drive ranges; automatic shift control means for controllingsaid range shift means to automatically shift drive ranges in accordancewith torque demand and output speed; manual shift control meansincluding power source means for controlling said range shift means tomanually select the drive ranges using power from said power sourcemeans and releasing control over said range shift means to saidautomatic shift control means on discontinuance of power from said powersource means; directional shift means for shifting between forward andreverse; and seqUence control means for controlling said range shiftmeans to discontinue the operating drive range during shifting betweenforward and reverse.
 9. In a control system for a power train providingmultiple drive ranges in both forward and reverse the combination ofrange shift means for shifting drive ranges; automatic shift controlmeans for controlling said range shift means to automatically shiftdrive ranges in accordance with torque demand and output speed; manualshift control means including power source means for controlling saidrange shift means to manually select the drive ranges using power fromsaid power source means and releasing control over said range shiftmeans to said automatic shift control means on discontinuance of powerfrom said power source means; and manual directional shift control meansusing power from said power source means for shifting between forwardand reverse and maintaining the selected direction for automatic rangeshifting on discontinuance of power from said power source means.
 10. Ina control system for a power train the combination of a plurality offluid-pressure-operated drive-engaging means each operable on fluidpressure delivery thereto to establish a drive range; a fluid pressuresource; a pair of governor means for providing a pair of governorpressures each increasing with increasing output speed; throttlepressure regulator valve means operatively connected to said fluidpressure for providing a throttle pressure increasing with increasingtorque demand; shift valve means corresponding to each of saiddrive-engaging means; said shift valve means operatively connected totheir corresponding drive-engaging means and operatively connected inseries to said fluid pressure source; one of said shift valve meansbeing responsive to one of said governor pressures and said throttlepressure to upshift and downshift and each of the other of said shiftvalve means being responsive to the other of said governor pressures andsaid throttle pressure to upshift and downshift to provide sequentialdelivery of fluid pressure from said fluid pressure source to saiddrive-engaging means to automatically shift drive ranges; manuallycontrolled shift controlling means for controlling each said shift valvemeans to manually select the drive ranges; each said manually controlledshift-controlling means comprising electrically operated valve meansoperable in an energized condition to establish an upshift biaseffective to immediately upshift the corresponding shift valve means andoperable in a deenergized condition to permit downshifting of thecorresponding shift valve means; an electrical power source; and meansincluding switch means for connecting said electrical power source toeach said electrically operated valve means.
 11. In a control system fora power train the combination of a plurality of fluid-pressure-operateddrive-engaging means each operable on fluid pressure delivery thereto toestablish a drive range; a fluid pressure source; a pair of governormeans for providing a pair of governor pressures each increasing withincreasing output speed; throttle pressure regulator valve meansoperatively connected to said fluid pressure for providing a throttlepressure increasing with increasing torque demand; shift valve meanscorresponding to each of said drive-engaging means; said shift valvemeans operatively connected to their corresponding drive-engaging meansand operatively connected in series to said fluid pressure source; oneof said shift valve means being responsive to one of said governorpressures and said throttle pressure to upshift and downshift and eachof the other of said shift valve means being responsive to the other ofsaid governor pressures and said throttle pressure to upshift anddownshift to provide sequential delivery of fluid pressure from saidfluid pressure source to said drive-engaging means to automaticallyshift drive ranges; a pair of fluid pressure operated directionaldrive-engaging means each operaBle on fluid pressure delivery thereto toestablish a directional drive; forward and reverse shift valve meansoperable in a forward apply position to establish fluid pressuredelivery from said fluid pressure source to one of said directions;drive-engaging means and in a reverse apply position to establish fluidpressure delivery from said fluid pressure source to the otherdirectional drive-engaging means; manually controlled directionaldrive-determining means for moving said forward and reverse shift valvemeans between said forward and reverse apply positions; sequence valvemeans for relieving fluid pressure from said furthest downstream shiftvalve means and corresponding drive-engaging means on movement of saidforward and reverse shift valve means between said forward and reverseapply positions; and forward and reverse shift inhibitor valve meansresponsive to said other governor pressure for preventing said forwardand reverse shift valve means from shifting between said forward andreverse apply positions in all of the drive ranges above the lowestdrive range.